Media playback is unsupported on your device Media caption Steve Rosenberg joins the brewers on their voyage

British brewers have sailed a beer-laden clipper to St Petersburg, retracing a centuries-old trade route. They hope to rekindle interest in imperial stout - once one of Britain's best-loved exports to Tsarist Russia.

Catherine the Great was proud she could drink as much of this strong, sweet beer as any Englishman Pete Brown, Beer historian

In the Gulf of Finland, a 60-foot British clipper glides towards the coast of Russia.

The sailors on board are normally more at home in a brewery than in a boat. They're brewers and beer lovers from across the UK. And down in the hold, they have a very special cargo: bottles and barrels of Russian stout - 14 different types in all.

It's a beer that 200 years ago Britain exported east in large quantities, particularly to the Russian imperial court - a trade that stuttered and then died more than 100 years ago due to war and revolution.

"It all started in 1698 when Peter the Great was on a tour of Europe and discovered a fondness for British beer in London," explains one of the crew, beer historian Pete Brown.

"When St Petersburg was built, British beer was served at banquets there and it was mandatory to drink it.

What does imperial stout taste like? Stout is synonymous with Guinness, but Imperial Russian stouts (and porters) are a different beast. Mad Monk brewed by Wigan brewery All Gates is a modern take on the strong dark beers that travelled east in the 18th Century. Guinness has a dry, bitter edge and less alcohol. These imperial beers are muscular heady brews, less bitter, many even darker than Guinness, and rich with the aromas of roasted coffee beans, milk chocolate, plums, currants and even leather. Some evoke childhood memories of tobacco boxes. Mad Monk, at 7.1% alcohol, has a mocha-like quality to the nose allied with a wisp of citrus. The luscious palate has coffee, chocolate, a burnt toast roastiness, plus a creamy and fat mouth-feel leading to a lingering finish. Lucky St Petersburg.

"Later on, Catherine the Great was enthusiastic for Imperial Russian stout. She was proud she could drink as much of this strong, sweet beer as any Englishman."

The stout needed to be strong. Beer with a lower alcohol content often froze on the journey over.

Some of the brewers on board have created their own versions of imperial stout.

And now they're hoping Russians will rediscover a taste for it. That could be good news for British business - and British diplomacy.

"We have lots of smaller brewers represented here," says project organiser Tim O'Rourke. "It may be really quite important for small brewers who are looking to expand and who are suffering a bit from sales in the UK.

"It's not an easy market for us to penetrate but I think this is engendering goodwill. It's almost like the ping pong diplomacy we had with the Chinese."

Once on dry land, stout diplomacy begins in earnest. At the giant Baltika brewery in St Petersburg, the UK brewers make a collaboration imperial stout with the Russians as a symbol of cross-cultural friendship.

Image caption The vodka flask of the Russian empress, who liked both drinks

The beer-makers from Britain are having a ball - they've been given party hats that make the men look like Peter the Great and the women like Empress Catherine.

But the big test comes later when the delegation decamps to an English pub with their own barrels of Imperial stout for a taste test.

As we wait for the beers to be tapped, Brown gives me another lesson in Russian/British beer history.

"Peter the Great left a trail of drunken destruction wherever he went. When he stayed at the diarist John Evelyn's house in London, to show his prowess, Peter the Great would lift up huge chairs in one hand and smash them into firewood.

"Then, when he'd drunk himself to the point of insensibility, his minders would stick him in a wheelbarrow and drive him through John Evelyn's flowerbeds and hedgerows and ruin the place."

Taste test

The Imperial Russian Stout begins to flow. And the Russians who try it, like it.

I think. "It tastes like tar and the sea," says one woman. "It's nice."

Image caption Beer sales are booming in Russia

A Russian man sampling the stout likes it too. But he sounds a note of caution.

"Like any European country, Russia is spoilt for choice when it comes to beer. We have more foreign beers in Russia than water in the River Neva."

Possibly. But surely none with such a rich and majestic history as imperial stout. Even if there are no emperors now to drink it, there are plenty of Russians who probably will.