REPAIRS are still being carried out on Barrow-built submarine HMS Ambush, more than six months after it crashed into a merchant vessel.

An immediate investigation was launched after HMS Ambush was involved in the collision while submerged off the coast of Gibraltar last July.

The submarine's bridge fin struck a shipping tanker while it was surfacing during a training exercise, in an incident which was described by the Ministry of Defence (MoD) as a "glancing collision".

Pictures taken at the time showed extensive damage to the fin, where some of the submarine's Thales sonar equipment is housed.

The Astute-class vessel suffered "some external damage" but no crew members were injured in the incident, which has left the Royal Navy with a repair bill likely to stretch to hundreds of thousands of pounds.

Just over a week after the crash, HMS Ambush sailed to the naval base at Faslane in Scotland where pictures published this month show the submarine still undergoing repairs.

A statement from the Ministry of Defence website after the crash said: "At approximately 1.30pm local time today, HMS Ambush, an Astute-class submarine, while submerged and conducting a training exercise was involved in a glancing collision with a merchant vessel off the coast of Gibraltar.

"We are in contact with the merchant vessel and initial indications are that it has not sustained damage.

"The submarine suffered some external damage but there is absolutely no damage to her nuclear plant and no member of the ship's company was injured in the incident.

"An immediate investigation is being conducted.

"The submarine will be entering Gibraltar for further checks. There are no safety concerns associated with HMS Ambush being alongside."

The Astute-class are the largest, most advanced and most powerful attack submarines ever operated by the Royal Navy.

The boat was involved in the collision despite being equipped with what the Royal Navy boasts are "world leading sensors".

The 7,400 tonne Astute-class vessels, which cost more than £1 billion each, carry torpedoes for targeting enemy submarines and ships and Tomahawk cruise missiles.

HMS AMBUSH: OPERATIONAL HISTORY

After being commissioned in March 2013, Ambush conducted an intensive period of trials in and around the UK.

In 2014 Ambush completed a full operational sea training package before embarking on her maiden Atlantic deployment.

During this deployment she represented the Royal Navy and the UK in Rio de Janeiro, celebrating the centenary anniversary of the Brazilian Submarine Service, and visited the USA where the crew worked with both US and UK staff in King’s Bay, Georgia, conducting multiple trials and ranging serials to prepare the boat for future deployments.

Ambush was docked alongside at HM Naval Base Clyde conducting a short maintenance period prior to deploying on operations. She arrived in Gibraltar in July 2016.