David Russell was the first Commanding Officer of HMS Vanguard, the UK's lead Trident submarine. He's a 30-year Royal Navy veteran of the submarine service.

In 2000, Commodore Russell led the British effort to save survivors from the sunken Russian submarine Kursk in the Barents Sea.He spoke to ITV News about his advice for anyone trying to adapt to lockdown.

If the restrictions in the UK continue until the end of June, Britain's national ordeal will have lasted for the same duration as an operational patrol by a nuclear submarine.

As I spent 24 years in the submarine service in the Royal Navy, people assume that I am “used to all this isolation stuff”.

In some ways I am, and here are a few thoughts and tips on emerging from this national emergency in good physical and mental health.

Over the last few months we have all become familiar with staying at home, sharing a confined space with others (with whom we may or may not get along with) and feeling wrenched apart from our normal world.

In a submarine there is, of course, no going out at all. There is no daylight. No vision of the world outside (unless you are one of the lucky few keeping watch on a periscope).

And no social communications with friends or families.

Submariners are pulled from family and friends for extended periods, and enter into forced companionship with others with whom they must live in close quarters.

And yet, somehow, it works.

If a fellow submariner gets on your nerves - there are other less savoury expressions for this - you simply have to find a way to deal with it.

You can’t walk away or decide not to see them again – you will be on watch with them for six hours, twice, each day for the next three months.

So, what lessons can we learn?

Lesson Number One:

Commodore Russell, left, with Colin Firth. The actor played the role of Russell in a recent film.

Accept the circumstances you are in and do your best not to annoy others or take offence.

Tough to do. We all fail from time to time. But it is essential to try.

Submariners also have their own version of panic buying. Before a long patrol - one that can often be extended by a crisis - stores are crammed into every conceivable space.

Spares, tools and most importantly, food.

You end up walking along false decks of tins in cardboard boxes and finding the space by your bunk crammed with loo rolls.

Sound familiar?

But at least on land we can pop out once a week on a foraging expedition to see whether there is any flour again.

Or adopt the old Russian habit of carrying a bag and joining any queue that forms simply to see what is on sale.

Not in a submarine.

If it isn’t on board, you have to go without. If something breaks, you fix it. If you have something, it is always shared.

Lesson Number Two:

The crew has to prepare for weeks on end in HMS Vanguard.

You can manage with less than you thought and still leave something for the next person.

Tedium can exist even on an operational patrol.

It is reduced to some extent by falling into the routine of six hours on-watch, six hours off-watch, which, after months on end, becomes the “new normal”.

Meal times and evening entertainment form part of that daily pattern of life in a submarine.

Chefs work in crazy conditions to produce great food and that does wonders for morale.

Showing a movie in the mess after dinner is more than simply watching a film. It is a social experience that allows tensions to ease and laughter to lift the spirits.

A trainee officer screwing up the screening of a movie, amid much banter and hilarity, is as much a part of getting along and being a team as going back on watch.

I should know. I messed up several film evenings during the era of the old “reel to reel” versions on rickety projectors.

Lesson Number Three:

These sleeping quarters inside HMS Vigilant show how tight space can be onboard submarines. Credit: PA

Social interactions are vital to our sense of identity and to maintaining our perspective and sense of humour.

Engaging with others - even if by phone, Zoom, FaceTime or talking across the street - is indispensable.

One way of carving out your own space when it doesn’t exist physically, is to have a hobby. I read a lot of books at sea.

I once took a marquetry set on a patrol but never opened the box.

This was probably wise as scalpels and thin bits of wood probably aren’t a good idea when the nearest hospital operating theatre is either a thousand miles away or the Wardroom table!

Lesson Number Four:

HMS Vanguard docked at Devonport, Plymouth. Credit: PA

If you have the space, a hobby is a good way of giving you some time to yourself, even when you are living very close to others.

I have now taken up baking sourdough bread and bicycle maintenance and am thoroughly enjoying both.

Physical exercise is good on so many levels of course, not only during lockdown.

It is possible to exercise on some submarines using bikes and rowing machines.

During my time in command of one submarine, I was passionate about circuit training (and if the Captain is a fan of something often it happens).

Several times a week the tables and chairs would be cleared from the dining room (the largest space but still tiny) and a make-shift circuit set up. Actually, it turned out that the crew loved it too.

Lesson Number Five:

Exercise is crucial. Credit: PA

Try to maintain or even increase your physical exercise. The size of the workout room doesn't matter. Improvise. It does wonders for the soul as well as the body.

Finally, as we see the first glimpses of light at the end of the lockdown tunnel, I confess I feel a little sympathy for our leaders.

As a submarine Captain, I would often have to tell the crew about unforeseen developments.

Frequently, it was bad news.

It might be an extension to the length of the patrol, or the abandonment of a much-anticipated port visit to conduct some secret operational task, which much of the crew would know little about.

So it is now for Britain. Boris Johnson and his ministers have to convey complex messages, many of which will be disappointing - even upsetting - to people yearning to get back to normal.

They are besieged by journalists seeking certainty.

But certainty doesn't exist.

As a submarine captain, the only way I could convey bad news and still retain the good-humoured support of the crew, was by being honest and admitting that I didn’t have all the answers.

So, now my final tip is for those in charge.

Lesson Number Six (for our political leaders):

Political leaders must be honest. Credit: PA

Be honest and be yourselves.

Anything less will not be authentic.

Without honesty and integrity there is the risk of losing the one thing you cannot survive without - the confidence of those you have the privilege to lead.