Tuesday morning and I pitch up at Martyns front door in South Wales for the TDI Overhead Environment Foundation/Cavern Course. I was joined by Rob, an amiable Trimix Certified Banker from London.

Martyn takes a refreshingly informal approach to teaching and for this reason captures your attention without the need for masses of slides and OHP's. After a quick slide show and introductory lecture the rest of the course was hands on.

The course has been specifically tailored to diving in UK style environments and Martyn is keen to point out differences in the kit required here as opposed to that suitable for warmer climes. For example, cute little reels with thin technical line (as sold by every diving retailer in the UK) are a menace in the UK where viz can be zero and hands are numb. Martyn introduced reels "A La Farr" - much larger with thicker line which was tagged every 10m in a way that could be felt by numb hands wearing thick mitts and also indicated the way out.

After a few minor tweaks to our kit we were off to the swimming pool (with the cover left on to keep the light out - clever) practicing line laying, blackout drills and air sharing prior to the dives on day 2.

Martyn used Dinas Quartzite Mine as a venue for the practical day. This Victorian mine that stopped production in the 1960's is about 600 metres from the road and about 40m above it so to save wear and tear on our backs we did a double load carry.

The water starts 80m walk into the mine and is crystal clear. After the dive brief we set off on our first dive, following a fixed line for about 50m. The layout of the mine is such that there are open water windows every 20m or so and the fixed line actually rises up to a higher level so that it is directly under an open air space.

On the next dive, Rob set off laying line as he went. About 30 metres later he signalled that he had reached "Thirds". We left the line in-situ and headed back to dive base.

After another dive brief and recalculation of thirds, me and Martyn were off again, back to the reel & further into the tunnel system. By this time the biting cold was starting to numb my hands and I was glad of the thick 5mm line we were using. Martyn's comments the previous day on the uselessness of thin line in the Uk were ringing very, very true. We reached our planned turn-point and I started to reel the line back in.

Problem...the split pin holding the spool onto the reel handle had disappeared and the reel was falling apart. At the time, I wondered if this was an intentional part of the course (later I was assured not). Whatever, I got the line back onto the reel in a fashion and surfaced a couple of minutes later.

Just enough air and digital dexterity left for one last dive. Martyn suggested a blackout drill but made it clear that this was not a required part of the sylabus but we could do it if we so wished. In for a penny in for £320 I decided to get my monies worth and off we went, retracing the route of our first dive to the first open water window. Here we switched our torches off and followed the line back to base in complete darkness. At one point, the line is caught under a railway track and does not form a perfectly clear route to open water. Not to worry, after feeling around for about 10 seconds I found the line and continued. Then my fin got caught in the line but after a few moments I was free again and rose gently to the surface.

During the dives, Martyn hung in the water above us and left us to deal with whatever problems occured (self dismantling reels, entangled fins, lost lines et al). Because of this I learnt 1000 times more through dealing with things myself rather than having the instructor being too keen to help out. To start with there were a few times where I wondered where he was but as I became more accustomed to the environment I realised that there was an orange light imprinted on top of the blue light from my LED torches and that he was watching my every move like a hawk.

What next? I am off to the local chandlers to buy a load of thick line and makings of a suitable reel and need to find someone to gain further experience with.

I would recommend this course to anyone wishing to progress their Overhead skills in the UK. Excellent!