...Originally our prototypes had an endurance of only 1.5 hours with 2.8 kg of lime. We came away from DERA, the Defence Equipment Research Agency (the Navy’s test house) with our tail between our legs. They told us in no uncertain terms our scrubber was underperforming. That was back in 1996.

We then started a development program which built six different types and styles of rebreather cartridge including both radials (fed both ways) and axial flow designs. We were told that with a radial design, if you flow gas in the centre tube so it passes radially out was the best due to the gas slowing at the outer edges increasing the dwell time.

Nice theory, but not that relevant, in fact we found the most significant advantage of radial scrubbers was not due to this at all , it was due to the insulation around the outside – the air gap between the cold canister wall which is chilled externally by the water, and the absorbent...