This clinometer was surplus to requirements on HMS Triumph

Contractors BAE Systems contacted Trinity Marine Ltd of Teignmouth in Devon when it needed clinometers as part of work on the �750m HMS Astute.

Clinometers are placed on submarines to detect if the vessel is listing.

The Ministry of Defence (MoD) said the items were being bought not to use on the submarine, but to help design and build a modern-day equivalent.

The MoD located these important components on the Trinity Marine website, more generally a source of nautical antiques and boat fittings.

HMS Astute is the first of the Royal Navy's next generation of submarines being built at BAE Systems' yard at Barrow-in-Furness.

The clinometers were surplus equipment on its predecessor, the Trafalgar class submarines, and were sold by the Ministry of Defence at auction. Now it wants them back.

We thought they were joking Matt Densham, Trinity Marine

Matt Densham of Trinity Marine said: "We thought they were joking, but they said they wanted 14.

"We only had seven, which we would normally sell for �200 each, but we felt it was our patriotic duty to part with them for a very reasonable �100 each."

One of the clinometers is from HMS Triumph, a Trafalgar class nuclear submarine launched in 1991.

Astute class subs - the first of which will be delivered in 2008 - will be capable of diving to 300 metres and will be able to run for 25 year without refuelling.

But the Ministry of Defence said it was keen to point out that its contractors were not having to use such dealers to actually kit out their latest vessels.

A spokesman said: "Clinometers are pieces of highly specialised equipment and no longer manufactured.

"BAE did not buy these to use them on board a submarine, but to use them re-engineer the design into something that can be built and used on new submarines."