THE fourth member of the Royal Navy’s powerful new Astute class of submarines achieved a significant milestone last week when she successfully completed her first dive.

HMS Audacious undertook her ‘trim and basin dive’ on January 10 at BAE Systems’ Devonshire Dock at Barrow-in-Furness.

HMS Audacious will be based at HM Naval Base Clyde, along with all the other Astute-class submarines, once her sea trials are completed.

The operation saw the high tech submarine submerge fully under water for the first time, enabling the mixed Royal Navy, Ministry of Defence and BAE Systems team on board to test many of the vessel’s systems.

The dive was a crucial milestone as it allowed engineers to calculate the submarine’s precise weight and centre of gravity.

Some 16 tonnes of lead were taken on board and moved across the width of the vessel so naval architects could confirm their calculations. The crew then dived 15 metres underwater to prove the safety and stability of the 7,400 tonne, 97 meter-long attack submarine.

Officially named in December 2016 and launched in April last year, Audacious is scheduled to leave Barrow for sea trials later this year. HMS Astute, HMS Artful and HMS Ambush are already in service, while Anson and Agamemnon, along with an as-yet-unnamed seventh submarine, are all under construction at the Barrow site.

-service with the Royal Navy. Boats 5 and 6 – Anson and Agamemnon – along with a yet un-named seventh Astute class submarine are in different stages of construction at the Barrow site.