WATCHED in the dark depths of the seas for months, our nuclear submarines are even more secret than the SAS.
Known as the Silent Service, their whereabouts cannot be revealed, images of high-tech interiors are categorized, and the crew never discuss their missions.
But now, thanks to the geniuses behind the hit TV series Line Of Duty, the strange world of the submariner is brought to the surface in the gripping BBC drama Vigil.
The six-part murder mystery, which drew six million viewers for each of its first two episodes this weekend, sees Suranne Jones play as a detective sent aboard a nuclear submarine to investigate a death.
But she struggles with claustrophobia and the psychological pressure of living in such a confined space.
Vigil’s set designers had to create their Vanguard-class submarine without drawings or photos, because their interiors are so secret.
So how realistic is that? Royal Navy veteran Captain Mike Davis-Marks, who spent 36 years aboard submarines, said: “They did a good job getting it right. I liked that.”
The 63-year-old from Kent is also delighted that the spectacle lifts the veil on the top secret world – a world whose contribution to defense is often overlooked.
He says, “It’s good to see what life is like inside a submarine, even if it’s a drama.
“There has never been a memorial worthy of the name. We have been too secretive.
As the series struggles to show, life on those billion-pound “cigar tubes” – which are the length of a football field and a half and four decks high – can be extraordinarily difficult.
Absent for three months at a time, the crew is never allowed to communicate with the outside world, except in cases of extreme emergency.
Sending any signal will compromise a sub’s position, meaning there is no streaming, internet or social media.
The work shifts are six hours, six hours off, repeated constantly, seven days a week.
“It’s good to see what life is like inside a submarine, even if it’s a drama
And privacy on board is rare, with bunks stacked so close together that your nose almost touches the one above.
Mike, who was in command of one of the nuclear-powered hunter-killer submarines tasked with searching for the enemy, says: “The submariners work 24/7. Often the only way to know what day it is is by the food you eat.
“There is usually a roast on Sunday, for example.
“Pull your curtain over your bunk and it’s dark. “
Father of two, he has been married to Tracy for 25 years. But when they dated while he was at sea, he says, she “wrote me 27 letters but never received a single letter in return.”
Silence is really the watchword of submarines.
The tools are attached to cords so that they do not click; there are twice daily checks for loose items; and Mike even asked his team to wear slippers.
He explains, “It’s about who has the quietest submarine. A quieter will hear the louder further. This is a very good cat and mouse strategy.
Even a death on board is no reason to come out of the depths. Mike says, “You wouldn’t pop up a submarine except in an emergency.
“I was in a situation where we couldn’t surface and had to sit down on bad news.
Absent for three months at a time, the crew is never allowed to communicate with the outside world
“A friend of mine commanding HMS Tireless had a mini explosion on board that killed two members while they were at the polar ice cap so that they could not surface in the Arctic.”
In Vigil, the submarine surfaces to allow DCI Amy Silva of Suranne on board to investigate the drug-related death of a sailor played by Martin Compston of Line Of Duty.
But Mike doubts the Navy will allow it – and even if it did, it wouldn’t be a civilian copper investigation.
And while he praises the series for capturing the tension and oppression of life on a submarine, there’s one thing that irritates him – the icy relationship between much of the crew.
He said, “You would never have that. If you don’t like someone, you learn to cope with them, so that the tensions don’t resurface.
“Being stuck in a cigar tube underwater for three months straight, you learn to tolerate everyone. Most people think we are crazy to do this.
“We just think we’re a professional part of the armed forces looking after it.”
Only eight years ago, the first women were also allowed to serve, and there are usually only eight out of a team of 120.
And there are strict “do not touch” rules, as DCI Silva de Suranne finds out when she approaches the coxswain.
Mike says, “You have the sex element on a sub, but we’re so close that I don’t think anything untoward could go on, everyone would know.”
Silence is really the watchword of submarines
The free time available to the team is spent sleeping, watching DVDs or participating in common activities such as quiz nights.
But they must be turned on at all times in an emergency. Mike remembers, “At 3 am, someone set off the flood alarm and we surfaced in an emergency.
“You can’t assume it’s not real. If you take too long to make a decision and there is too much water in it, it won’t go up.
When the submarines were first launched by the Royal Navy in 1901, Admiral Arthur Wilson described them as “submarines, unjust and cursed non-English”.
An Astute class fighter killer submarine is currently following our £ 3.2 billion aircraft carrier HMS Queen Elizabeth to the Far East and a Vanguard class is loaded with Trident nuclear bombs somewhere.
Mike now wants a proper tribute to those who lost their lives in submarines and is part of the Submariner Memorial Appeal, supported by Prince William.
They’ve raised £ 440,000 of the half a million they need – and an 11-foot bronze sculpture has already been designed.
Mike concludes: “I think we’re a bit of a victim of our own self-preservation instinct.
“Like special services, we don’t talk about what we do.”
The vigil continues Sunday on BBC1 at 9 p.m.