Nuclear sub is nearing completion

The Astute sub is under construction in Barrow

Britain's latest nuclear submarine - being built in Cumbria - is nearing completion, defence officials say.

HMS Astute, constructed at Barrow, will be the Royal Navy's biggest, most powerful attack submarine ever.

Weighing 7,800 tonnes - equivalent to 1,000 double-decker buses and almost 100 metres (328ft) long, it has more firepower than any previous attack sub.

It is due to be launched next year and will be based with the Vanguard Class subs in Scotland from 2008.

It is the first of three Astute Class submarines being built for the Navy.

Nuclear reactor

The Astute is different to the defensive Vanguard Class subs, whose Trident nuclear missiles carry Britain's nuclear deterrent.

As an attack vessel, its Spearfish torpedoes and Tomahawk cruise missiles are capable of delivering pin-point strikes from 2,000km (1,240 miles) with conventional weapons.

Around 6,000 workers, including an army of engineers from BAE Systems, have worked on the £3.8bn project, described as "more complex than the space shuttle".

Powered by a nuclear reactor it will never have to be refuelled during its 25-year life, can manufacture its own oxygen from sea water and is capable of circumnavigating the globe while totally submerged.

Work to piece together the hull of the vessel was completed ahead of schedule in December.

The yard, which has been criticised in the past for late completion of projects, has been involved in the construction of all three Astute submarines.