The celebration dives took place at the National Diving & Activity Centre (NDAC) on 4 April, three days after the first of those landmarks.

The Gloucestershire inland site was chosen as being accessible from Brize Norton and having the required maximum depth.

NDAC provided exclusive access for the dive-team and any other RAF Sub Aqua Association branches, with RAF Odiham SAC taking the opportunity to carry out training dives.

The Brize Norton team consisted of 14 service personnel who dive as part of the RAF’s Adventurous Training package. Diving to Ministry of Defence regulations required special permission to dive beyond 40m and official supervision of the project, which had been six months in the planning

In the event the team fell short of their target because of members’ operational commitments, but still managed 26 dives between 15 divers from both clubs.

Sgt Chris Worrall described the 50m signature dive with his buddy Phil: “We descended, torches on illuminating our surroundings, passing 20m, a stop to check kit and signal OK, passing 30m, another check, slowing at 40m.

“We signalled OK, left the shotline and descended further into the quarry, seeing the small cabin-cruiser emerging from the eerie darkness. This was the planned backdrop for our 50m photo. Our computers sounded 50m; we had reached our destination.

“I unzipped the pocket containing the RAF ensign; no sign of nitrogen narcosis. I unfolded it and we posed for a photo.

"Just five minutes at the bottom and we were into mandatory decompression ceilings – time to start our ascent. As we approached the decompression trapeze, our drop tanks came into view, we relaxed and out came the ensign for more photos.

"We cleared our deco and shook hands – a dive to remember. Just 6m of water above us now. We ascended slowly, breaking the surface 32 minutes after we left it.”

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