Royal Navy submarine HMS Tireless has arrived in the southern Indian Ocean to help in the search for missing Malaysia Airlines flight MH370.
The Trafalgar Class submarine arrived yesterday in the area – the focus of the search for the missing Boeing 777 – where it will help in the hunt for the plane's flight recorders.
Flight MH370, bound for Beijing from Kuala Lumpur, disappeared on March 8 with 239 people on board, with a three-week search finding no sign of it.
The search area, which has repeatedly shifted as experts analyse radar and satellite data, is currently focused on a 98,000-square mile area off Perth, Australia.
Royal Navy survey ship HMS Echo is due to begin search efforts tomorrow, but a source said that Defence Secretary Philip Hammond has called his Malaysian counterpart to say that HMS Tireless has arrived in the area, where it is searching for the flight recorders.
The source said: "In addition to the deployment of HMS Echo, a Royal Navy survey ship, which begins search efforts tomorrow, a Royal Navy Trafalgar-Class submarine has recently arrived in the area and is conducting search operations for the flight recorders.
"She was ordered to move from an operational tasking to the search area around a week ago and arrived on station yesterday.
"HMS Tireless holds advanced search capabilities, but the task in hand remains a tall order and the search area is immense. Her deployment is being co-ordinated closely with our Australian and US colleagues.
"The Defence Secretary informed his Malaysian counterpart of the additional British contribution during a phone call this evening."
HMS Tireless has advanced underwater search capability which it is hoped will help in the hunt for the missing jet.
It is just one part of the UK's contribution to the search, with HMS Echo due to arrive in the southern Indian Ocean to help in the hunt for the plane's black box, as well as helping in the search for debris on the surface.
Britain is also helping with technical assistance and specialist capabilities from across the Ministry of Defence, the Hydrographic Office, Department for Transport and the Met Office to help try to find flight MH370.
Four RAF personnel on secondment to the Royal Australian Air Force and Royal New Zealand Air Forces are also actively involved in maritime search operations.