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"And it's a tail-first layout called a canard so it's got the tail at the front. The all up weight is 750kg but 240kg of that are batteries so all the structure is carbon fibre to keep it as light as possible," Dr Brooks says.

His carbon fibre creation, known as VX4, has eight propellers and looks like a giant drone, but what's crucial is that it doesn’t use fuel.

He’s already used to his carbon fibre limb and is even training for next year’s Invictus Games.

The hull’s material attracted the most attention - it was made from layers of carbon fibre mixed with resin.

Roy Thomas from the American Bureau of Shipping said carbon fibre was not approved for deep sea subs because it can weaken with every dive and fail suddenly without warning.