I have been privileged and lucky enough to be involved in some of the most advanced and exciting dive projects in the world. My gear has developed alongside these expeditions, and certain equipment was even designed for specific projects.
Everything I use has been tested, from the extremes of flooded French caves to 160m-deep wreck dives way offshore in the Atlantic. I have to put total confidence in my kit and, while I still wonder if that kit is the best it could be for my diving, its probably as close as it needs to be.

I am fortunate to have access to eight units, but number one choice is the CCRB Sentinel, followed very closely by the AP Diving Evolution Plus.
Both are made in the UK, which makes using them that much more satisfying. The APD unit has been involved in more expedition dives than any other unit I know, and in 2001 I took a standard Classic Inspiration on the first-ever dive on RMS Carpathia, which lies in 160m - praise indeed!
The Sentinel became the solution I was looking for last March, because having a back-mounted rebreather made handling large numbers of stage cylinders so much easier. The work of breathing
and advanced features makes it a firm favourite with advanced divers.
I have been known to use a Megalodon on demanding cave and/or overhead-environment dives. The lack of a CE mark makes it impossible for me to use it commercially, but its a formidable unit that is incredibly reliable and well-made.

I have used only one type in my career, an Otter Britannic Telescoping Torso suit. I have never been
a fan of neoprene suits. Even the crushed type all seem to suffer from buoyancy loss at depth.
Most students I come across on courses seem to be underweighted on the deco phase, and heavier at depth. The membrane variety from DUI and Otter dont suffer from this, so I find buoyancy control much easier.
Warmth is not an issue if you layer up correctly, and with the layering system you can make the membrane suit far more flexible in temperature extremes.
My Otter has been in 26°C water while decompressing on the Britannic, and 1°C water in Finland. Its only the undergarments that change.

With pants in mind, lets move on! I mostly use Fourth Element thermals, a combination of standard Zero Therms under a set of thicker Arctics for most UK summer diving and dives up to three hours long.
For longer dives, a C-Bear undersuit goes over the Fourth Element gear to keep the heat in. A heated undervest may come out, but its got to be really cold for that! Ive found that the Otter double hood system keeps my head incredibly warm, and the water trapped between each hood actually warms up during the dive, like a good-fitting wetsuit.
I also use Swedish Navy dry gloves. I have holed these only once in 18 months, testament to their incredible toughness.

Ally stage cylinders are the only type that work for me, and I have nearly 20 different ones of between 5.5 and 11 litres. The job dictates what I take, but every cylinder will use a Poseidon Cyklon regulator with 1.2m hose, to make emergency gas-sharing stress-free.
Each regulator also has a low-pressure inflator hose, allowing me to inflate lift-bags, counter-lungs, drysuits and even my wing if necessary. There is also a 15cm hp hose with SPG on each reg set.

Since 2003 I have used a VR3 with the VPM upgrade in support of a decompression software program called GAP. Most modern rebreathers have in-built software, so the VR3s and more modern VRX from VR Technology are used as back-ups to the onboard information.
Modern technology cant be 100% reliable - though it generally is - so I still take a standard Uwatec depth gauge and underwater wet-notes for back-up deco information.

I prefer the Silent Submersion N-37, the ni-mh-powered version of the tried-and-tested UV-26
lead-acid scooter, which is favoured by serious cave-divers worldwide.
The N-37 is a compact, reliable unit giving more than 90-minute burntimes, with a proven depth rating of more than 150m - more than good enough for me! It may not be the most technologically advanced scooter, and certainly isnt the fastest, but it has a deep wreck- and cave-diving track record that other units will never have.

Salvo and Halcyon HID torches provide primary lighting, while Halycon Scout torches provide back-up. Dive Rite reels have always been my favourites, and I use the free-flowing spools for DSMB deployment.
I use the low-pressure hose inflating style DSMB in red for drift decompression, with the same in yellow in case of emergency.
Finally, forward propulsion when not using a DPV is by a pair of 10-year-old Scubapro Jetfins, and the ability to see under water is made much easier by a Scubapro frameless mask, also nearly10 years old.