Devonport workers entombed in submarine ballast tank

Two workers were accidentally entombed inside the ballast tank of a nuclear submarine, it has emerged.

Colleagues had mistakenly sealed the tank at Devonport base in Plymouth, where Britain's nuclear submarines are refitted.

The desperate electricians hammered on the tank with a drill and were saved when they got a faint signal on a mobile phone.

The Unite union called it "an extremely unpleasant situation".

The men were inspecting sonar gear in the ballast tank

A report said the submarine was in dry dock last December and the two men were checking sonar gear inside the ballast tank.

When they tried to leave they found a seal had been placed over the entrance in preparation for an air tightness test.

It said: "In an attempt to raise the alarm they used the only thing they had to hand - a battery powered drill to hammer against the tank boundary but to no avail.

"There was no-one in the dock bottom to hear them.

A report said the men escaped "shaken but unhurt"

"They switched on their mobile phones but there was no signal at the bottom of the tank so they progressively climbed to the upper reaches of the tank until fortunately one phone managed to get a one bar signal."

Twenty minutes after their ordeal started, the men were freed "shaken but unhurt".

Unite said: "We feel for the men involved and what they had to go through because it must have been an extremely unpleasant situation.

"The incident was actually caused by poor management and poor communication.

"We are disappointed it was not in line with Babcock's normal standards."

Babcock said it was "continually focused on delivering and maintaining the highest standards of safety procedures and practices".

It said an internal investigation was carried out and "changes to work control arrangements have been made".