The BBC drama Vigil has become one of the most-watched TV shows this year.

The final episode aired on Sunday September 26, bringing an end to a series that has brought to life the secretive world of submarines.

The series has all the hallmarks that make for a great drama - murder, espionage and forbidden relationships.

But how realistic is the show?

North Norfolk News: Robert Glover served on submarines in the 1970sRobert Glover served on submarines in the 1970s (Image: supplied)

Robert Glover OBE, 64, from Aylsham, is a former submariner who served on vessels in the 1970s. The submarines were very different from the hunter-class nuclear submarine depicted in Vigil, but Mr Glover still saw similarities to his experience in the Royal Navy.

"It wasn't like the floating hotels they have today. Lots of people suffered from claustrophobia. It wasn't easy. I worked on smaller diesel submarines with 60-70 men. And at 6ft 2, it got very cramped.

"After two weeks at sea there was no more water for washing so it became a very dirty and smelly place. All you had was your bunk and sleeping bag, and the longer you were at sea the worse the food got.

"People were allowed to smoke on board then as well, so you had the diesel fumes mixing with cigarette smoke."

North Norfolk News: The final episode of Vigil airs on Sunday September 26The final episode of Vigil airs on Sunday September 26 (Image: WARNING: Use of this copyright image is subject to the terms of use of BBC Pictures' Digital Picture Service (BBC Pictures) a...)

While living conditions were different, there are some aspects that Mr Glover could relate to.

"The experience in the control room is quite similar. I served during the cold war, and there were some very tense times. If we picked up other vessels on sonar we'd have to stay very quiet and morale would drop. But once they moved on we'd crack open a beer."

Lines of communication to home were unavailable to submariners while at sea, but there was some news they simply could not go without.

"One tradition was that we'd head towards the surface at 5pm to periscope depth and raise the radio mast so we could get the BBC World Service for the football results without getting detected. With a crew from all over the UK, it was always great fun, depending on whether your team won of course."