The sight of an ex Tory minister descending into the bowels of a Russian submarine moored in British waters is nothing surprising amidst a week of Brexit-inspired parliamentary madness.

But the former MP in question here - Michael Portillo - is long-retired from politics and tomorrow night he'll be seen on TV visiting the former Soviet vessel moored in the Medway at Strood as part of his new documentary, Portillo's Hidden History.

Airing on Channel 5 at 9pm, episode three of the series sees the former cabinet minister turned TV presenter step aboard the 300 foot Soviet Foxtrot-Class submarine, and explore its role in the Cold War.

Writing in the accompanying book Portillo’s Hidden History of Britain, published by Michael O’Mara Books, he tells of his visit.

"On a suitably murky day I went aboard and, with the help of a vice admiral of the Royal Navy and two former Soviet naval officers, relived some of the most perilous moments in our nation’s history.

"The submarine is moored on a loop of the Medway at Strood, with the Norman-era Rochester Castle looming on the east bank of the river beyond the road-and-railway bridge. The castle was built to protect against foreign invasion in an age of rudimentary wooden ships propelled by wind and oars, crewed by men armed with swords. The Foxtrot-class sub had ten torpedo tubes, could dive to a depth of nearly 1,000 feet and was capable of remaining submerged for up to ten days at a time.

"The one I was about to explore had seen better days. As I approached on a river launch and it materialized through the mist, the phrase that came to mind was ‘rusting hulk’. Scaffolding covered the conning tower and its vast, bulbous-nosed bulk had the air of a mortally wounded beast. But what a beast it had evidently been. Even in a state of dilapidation this old bruiser of the Cold War exuded menace and defiance."

Watch the rest of Mr Portillo's adventure in Strood tomorrow night.