The location of the stricken Kursk

"You are just relying on all those special ingredients of a submariner coming in to play at a time like this," says

"It will be a case of the strong helping the weak, sustaining each other.

"I would hope that they [Kursk's crew] have got themselves into a routine, and are trying to make themselves as comfortable as possible. They will be trying to make not too much movement, they have got to think about their carbon dioxide levels."

An essential part of the make-up of a submariner is an instinct not to panic. In part this would be a natural reaction, says Commander Tall, because they would know there was nowhere to run.

"Submariners need not panic. This is where their whole training kicks in."

Being underwater would not be, in itself, a problem, as submariners are used to it. Royal Navy submarines stay beneath the surface for up to three months.

HMS Repulse, a Polaris submarine, formerly commanded by Jeff Tall

"It's not a problem, you become completely adjusted to it. My wife says I'm never happier than when I see the lid close. You are running a small town underwater."

Conditions on board have improved hugely in recent years, he says, but "there's still the same conditions of proximity and no privacy. So you do have to be a particular type. I just hope the Russians are that kind of type."

International camaraderie

If he were in charge of a British submarine in the same situation, Commander Tall says he would maintain his morale with the knowledge that the Royal Navy was doing everything to get him out.

"The Russians have the right to expect that their navy is doing the same. And what's encouraging is that the US and UK have offered to help.

"There is a camaraderie between submariners all over the world. We know what makes him tick, whether fighting him or just watching when something like this has gone on."