Back in 2019, Jon Glanfield completed his IANTD Full Mine Diver course and put together this article describing the events of the course in great detail. It's an extensive read, but one that we feel would help illustrate to interested divers exactly what is involved in the course if they are looking to get into UK mine & cave diving.


So following on from a brief 4 days of intro to mine, the main event finally rolled around in early June and I was looking forward to 5 days of mental and physical challenge expanding my skills and opening up a new strand to my sub-surface adventures.

Just to backtrack slightly, at this stage of my 2nd diving career I had been diving CCR pretty much exclusively since my renaissance, but due to irritating issues like CE marking, HSE regulations and a relative dearth of instructors available on KISS units training in the OHE on my CCR would be problematic.

I was also keen to use someone relatively local for training for logistical reasons and to provide an insight into the most easily accessible mines from home so that there was an onward progression path available once qualified.

This would necessitate a return to OC, which I was secretly actually looking forward to, my untimely departure from the aquatic world in the 90’s pre-dated the wide acceptance of Hogarthian rigged doubles and I was DIR curious. Not only that there would be transferrable knowledge in terms of SAC, swim rates on OC and stage juggling skills that would underpin bailout planning on CCR.

I had also read much on the debate of whether it was preferable to start the OHE on OC and then transition to CCR or if CCR trained go direct to the OHE on CCR and my preference was the former.

Luckily one IANTD’s leading lights in OHE training lives around 30 minutes from me and thus it was that I was able to tap into Ian France’s extensive knowledge of all things dark and submerged, covering access, skills, dive/gas planning and future development and use of newly acquired abilities.

Day 1&2:

“Fool of a Took!" he growled. "This is a serious journey, not a hobbit walking-party. Throw yourself in next time, and then you will be no further nuisance.”


3 of us had completed the intro section of the evolution, but only 2 of us were going on with the full course. Mike and I had managed a dive in between the 2 courses which helped to quantify the original course learning and cement our diving partnership, and so it was that we rocked up at the diminutive but perfectly formed Holme Bank Mine in Bakewell.

Well I say perfectly formed, but for the two of us at over 6 feet, the initial access route is tortuous, especially with a set of doubles, simultaneously trying to avoid rolling on a valve and venting precious gas but at the same time not pitching face first into the splintered chert deads all over the floor.

Mercifully perhaps day one was dry side skills, re-enforcing line laying, locks and, placements, introducing simple and complex navigation considerations and protocols and rehearsing lost line and entanglement scenarios. All completed in the decaying sheds that would have been a hive of industrious activity prior to the mines closure in the ‘60’s.

Day two was a wet day, and actually transpired to be something of a car crash in terms of showcasing my diving skills. The plan was a simple traverse using jumps, some line laying, a circuit and finally a blind entanglement scenario.

Simulating zero vis in Holme Bank

For those that haven’t been Holme Bank is shallow at the best of times, coming off the dry winter and balmy spring it was almost a swimming pool with a feature roof. Naturally this would challenge anyone’s buoyancy skills (or so I like to think) as you can be in circa 1m, trying fastidiously to hold trim, remove a spool, tie it in, place a marker, signal and then make the jump. I was all over the place, all day, systematically undermining any shred of respect I may have built up in Ian’s eyes initially, to the point that he laconically pointed out afterwards that he had “seen both of you dive better”.

My highlight was the entanglement drill which culminated in me cutting the line on the wrong side, and subsequently watching Ian point a symbolic handgun at his temple and drop the hammer.

Anyone for golf………………

In my defence that night repairing various broken items of kit including a spool and a leaking second stage diaphragm I did find the Schrader in the inflator loose so was probably inflating the wing all day but with the task loading and limited volume ingress I probably didn’t twig. I also consoled myself that it was far better to have stuff go belly up in training and learn from it than to become complacent because you are a diving ninja in front of our seemingly understanding instructor in the forgiving, crystalline waters of HB.

In spite of my performance Ian confirmed that we were on for the mines……………

Day 3

“Moria...(North Wales) You fear to go into those mines. The dwarves delved too greedily and too deep. You know what they awoke in the darkness of Khazad-dum... shadow and flame.”

Sorry, been done before but couldn’t resist.

So it was that we found ourselves at Aber Las, a slate mine that foundered due to the falling markets and a rising flood during the 40’s, in the rolling hills above Langollen.

It is factually a continuation of the much larger and deeper Cambrian mine whose entrance is less than a kilometre from AL, but diving operations only started there after a chance discussion with the landowner back in 2013, sadly the original explorer was to lose his own life in the mine in a tragic accident during the explorations and a plaque to commemorate Will Smith’s contribution to the mine diving community rests in memorium above the head pool.

Whilst the quote from Tolkien is all atmospheric and foreboding as befits these dangerous undertakings, something from Alice in Wonderland might be more appropriate given the access point. As part of the site briefing Ian led us up and through a small copse to reveal a hole, bordered by vegetation and tree roots no more than 2m square, into which we would be heading. Once a ladder had been rigged, this revealed the decrepit remains of a slate stair case leading off into the dank darkness of the access adit below. To the right partially obscured by the soil detritus of the intervening decades, lay a winding drum and the rusting ends of hawser cables that would have pulled the stone to the surface and far below the stairs ended and the water began.

Ladder entry into Aberlas

Today’s objective was a twin and stage dive in the shallow route, involving a series of jumps, a stage drop, a brief excursion to the deep level down the fabled (in certain niche circles) Stairway to Heaven and then a linear return on the route we had just created. This would be a set up dive for a circuit via the deeper level the following day. Stoked wasn’t in it!

With his usual gentle and stress free demeanour Ian outlined the dive, discussed our queries and observations and then it was time. Of particular note was that the initial access into the levels from the head pool would be in very limited potentially zero viz, owing to the gravitational movement of the slate debris that is dislodged on the way in, either via the continuous streamway adjacent to the stairs, or just from traffic in the head pool.

It was bad but not as bad as it could have been evidently, and after what seemed to be a pretty short drop we were into the clarity of static water surrounded by the rough-hewn rock, partial walls and industrial detritus of the mine and I can honestly say I was blown away. We glided through the tunnels in excellent visibility, nosing our beams into far off chambers and voids, following the plan, staying in trim and at all costs avoiding the horrendous silt of slate dust that adorned every surface.

Mainly we were successful in this endeavour, unfortunately we did manage to hit the stage switch point in a twisting, slightly small tunnel, eager to follow our dive brief we duly dropped the stages and an in so doing might have disturbed the silt….a bit. Owing to the confines of the tunnel it contrived to hold it and was still slightly in evidence the following day.

Typically seconds onwards and we emerged into a room that BOC would have happily used as a cylinder depot, but hey we were new here.

All the while Ian watched, lights off from the darker recesses of the mine, periodically he would glide silently out of the gloom equipped with his little Triton chest mount to bark directions or instructions into the incongruously translucent blue, breathing tubes. Loaded out with twin steel 7’s this was an impressive piece of kit and I was getting ever more green eyed about the whole thing, especially as it is so perfectly suited to this high effort access style diving.

Anyway, I digress, part way through we swapped leads so that both of us were putting in jumps and finally we made the eagerly expected connection to the line into the deeper section.  Deeper is relative in fairness, we are only talking 20m but the ambience, large quantities of rock and 300m swim before you can surface meant it would feel deeper.

We pressed on down the stair case, dropping like fighters in formation, a mine cart appearing out of the darkness, still sat on it’s rails like an exhibit in some slightly damper version of Beamish Museum, ahead the lower tunnel intersected the stairs as a T-junction and our final jump tied into the seemingly fragile thread link that could lead us back to our world.

Aberlas Staircase
Descending the "Stairway to Heaven"

As planned we pulled wet notes and noted time, depth and gas so that on the circuit we could ascertain whether on arrival here from the opposite direction, we could safely proceed with sufficient reserves to exit via our spool strewn route.

There then followed a slight breakdown in communication, we had tentatively planned to consider and recalculate thirds at this point, and with sufficient margins a small excursion towards the end of line in the deeper section could be feasible.

This however got lost in translation and we ended up on the ascent back up the stairs en route to home. With less task loading on the return trip we got to appreciate the surroundings more and after a low stress, gentle meander we picked up the stages, screwed the viz even further and mustered at the base of the entry chute, before making touch contact with the line to exit through the cloud of slate dust suspension.

Day 4

"The wealth of Moria was not in gold… or jewels…"

With increased familiarity the following morning our efficiency levels were higher and in short order we were in the head waters again, clipping off torches, hanging stages and completing real world S-Drills. Our entry route this time was left of the tie in to the mainline and would descend relatively quickly to the 20m tunnel.

Again visibility wasn’t brilliant but I could still discern the shape and tightness of the shaft and also made out some tally marks on the wall scratched by the workers so many years before. I emerged into clarity in time to see Mike negotiating the tight right hander and we were off on our long swim to find our tie off.

This tunnel was slightly smaller than most of the shallow route, but it was all lined so task loading was reduced, it was on this swim that I had any inkling of a head space issue and early on the slightly more claustrophobic conditions, volume of rock overhead and general situation weighed heavily on my consciousness, I concentrated on slowing and deepening my breathing and gradually dissipated the feeling.

Along the route again we would emerge into sections where the chambers opened up around us begging for return visits to unveil their secrets, all around and through the evidence of the mining is still present, cable rolls, points switching gear, pinions and rails, so a bit like cave diving but with the human interest of a wreck thrown in for added frisson.

Eventually our final spool from the day before appeared and we noted time to calculate swim times later, checked gas against known requirements and agreed we could make the round trip, which also meant no stage drops mercifully from a clarity perspective.

We were the embodiment of efficiency on the return fully channelling the WKPP (well I can dream), confirming cookies, sharing light, picking off the spools and making progress and then all too soon we were back at the junction between 5mm braided line and polyprop signifying the exit ramp.

A light debrief with Ian and his ever present white board, a quick dry side demo of some exercises for Mike to hone is back fin and plans were made for Cambrian which would be our final days destination.

Day 5

“You shall (cannot for the nerds) not pass”

That would have worked so well if one of us had failed………………..

That said I am not sure Ian could have pulled off a convincing Gandalf impression, there are some uncharitable souls who have suggested a passing resemblance to the Gingerbread Man, but I couldn’t find any quotes that would work and it would have ruined my Tolkien thread anyway.

Day 5 was much more welsh, a steady drizzle was rapidly becoming a downpour, which judging by a quick look at the access to the mine was going to create a health and safety nightmare, I did ask to see the risk analysis but I’m still waiting.

Cambrian is altogether a more impressive and imposing site in terms of access, appearance and magnitude, a short walk through rapidly dampening woodland, lead to a left fork and a view of the great maw of slate fanged darkness that opens up out of the fringing bracken, creepers and trees looking for all the world like a scene set from Jurassic Park.

The final footpath, if you can call it that descends steeply over loose rolling gravel and exposed roots before culminating in broken ground littered with huge shards of slate that have fallen from the entry way over eons of freeze thaw activity, splintering the rock and crashing it into the path of intrepid mine explorers. With ever worsening top side conditions we rigged a makeshift hand rope from bits in my van, to assist what would be a treacherous access route with a twinset, but a piece of piss in a chest mount, no hard feelings Ian honest.

Just beyond the rubble of the entrance the first indication that this has industrial heritage appears in the form of small submarine sized air receiver, studded with golf ball sized rivets as befits its age, abandoned to the ravages of nature and time. The remains of huts are also evident, some crushed under the weight of falling blocks from the roof which was now far above.

As we gained an insight into the numerous potential dive bases, 5 in all, Ian pointed out the prehistory of the mine as evidenced by a clear layer of greyish white ash in the slate strata laid down during volcanic activity before the ages of man.

This was to be another traverse, facilitated by a very short first dive on a stage to set up a reel at a 4 way line junction at 16m leading back to a tie off at DB 2. We then ditched the stage, wandered fully kitted through the dry passageways and re-entered at DB 3 to through dive back to the 4 way and reel connection. All being well we would then recalculate gas and head off for a mooch.

Cambrian’s general ambience continues below water, it’s vibe is altogether more committing, it’s size, depth, maze of networking tunnels, huge rooms and varying visibility due to the river feeding into it all contribute, our route lead us into chambers sometimes at half height, allowing a drop into the void with barely a sight of the rock walls and roof that you sense are there but can’t make out in the gloom.

Carefully marking each intersection, in case we had to return, we noted the proliferation of tees in place of jumps and a much less ordered and poor quality of mainline placements, tautness and layout generally.

With Ian’s guidance and pointers on route finding we advanced through to our first objective, a line of abandoned mine carts with an intersecting line leading to our tie off. We ascended gradually to confirm the line was intact and complete, before recalculating thirds and agreeing a new turn pressure, then it was back into the deeper reaches at around 27m to explore further. We moved our marker to denote the revised exit route and swam east passed more carts, the base of a staircase equipped with a jump and other enticing side shoots and options.

Ascending the staircase in Cambrian

With a degree more freedom afforded to us, we turned and made our way back to the carts before picking another northerly passage, crystal clear, still lined with rails and waterlogged sleepers. After 3 days of diving, air in the back mounts and a bounce to set up the traverse my gradient factors were clocking up time at the 6m stop. With the swim back and line recovery to undertake, and burgeoning decompression obligation I decided to turn the dive ahead of the agreed pressure.

By the time we reached our staircase exit route and had recovered the reel, and ascended to 6m I had around 18 minutes of stops, as part of the learning process I now realised that a 6m final stop setting works well in OW but can be a bit limiting in a mine, I was wedged on the stairs, fins on the bulkhead, face in the slate, dry (well wet) stone walls at each shoulder. Had I had the intelligence to change to a 3m last stop, I could have relaxed amongst the slate rubble above with room to spare and the opportunity to move about, keep warm and improve off gassing.

Time passed as it inevitably does and we surfaced into the cold, brackish gloom of the head pool, its sheer size and darkness absorbing much of the light of our torches.

And that was it we were done, well aside from the herculean task of removing the kit from the mine and de-rigging the access ropes in the torrential deluge of course.

Ian congratulated us, and given the worsening conditions we packed up and left. 5 days, 3 mines, 7 dives and 2 newly minted OHE divers.

Throughout the week we were admirably supported in terms of logistics by Frogsborn on Deeside who were more than accommodating pumping cylinders well before official opening time and very close to closing.

All through the course Ian’s easy manner and wealth of experience and exposure came through, his approach was inclusive but gently steered us towards the simplest of solutions and real world applications which could or would work best in the environs we had experienced.

It’s a tough course both in terms of skills, knowledge, environment and not least physicality, hauling 30kg plus of gear down and up shattered and rotting adits isn’t everyone’s idea of fun, but the rewards are there and it opens up a new vein in terms of diving options especially over the long winters where the below ground air and water temperatures can be much more conducive than inland or offshore sites.

Looking forward, we have a lot of simple mainline diving to do to cement everything and Ian has some interesting developments in respect of correctly ordered and organised archaeological surveys to document and chart certain mines, in addition to re-lining or improving the lines where necessary. Hopefully we can be involved as we build our skills base in the darkness of Khazad-dum.

Author, Jon Glanfield


1 Comment

  1. A very absorbing article extremely well written. I could feel my adrenaline kicking in, and I’m reading this at home sitting in the sunshine.

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