A startlingly tart apple crumble is my traditionally British dessert, as I sail towards Scandinavia and Russia with one of the world’s most venerable old cruise lines.

Yet on the MV Britannia, P&O’s new flagship liner, the familiar dish is turned on its head.

The crumble looks like breaded cod and is accompanied by a bowl of ‘mashed potato’ – a sorbet tasting like 100 apples have been crammed into every icy spoonful.

With celebrity chef Marco Pierre White on board, I feel I could be in a select corner of an English shire, enjoying the fruits of a same-day forage in his beloved orchard.

He’s just one of the kitchen whizzes P&O have recruited for a star-studded line up of Food Heroes Cruises. Indian cuisine specialist Atul Kochhar, French master pastry chef Eric Lanlard, wine expert Olly Smith and Brit boy James Martin also host voyages, and some are even prepared to roll up their sleeves and teach passengers in the ship’s Cookery Club.

I’m sailing on Britannia, the largest cruise ship ever built for the British market. The 3,600-passenger monolith is based in Southampton and its Union Jack livery is visible for miles when at sea. It towers over far-flung quays like a piece of oceanic mega-fauna.

Eric Lanlard has joined us for this sailing, creating a gourmet version of that most British of institutions – afternoon tea.

I munch tender roast beef and horseradish on brioche, marvelling how the delicate peppery taste of watercress is preserved. It’s followed by a cheese ‘eclair’ of Brie and sweet red onion marmalade.

Star of the show is a dark chocolate ‘tear drop’, my spoon revealing a centre of oozing Italian Amarena cherry mousse, and I can’t help but remark on the clever presentation, as I bite into a rose-flavoured cake in the form of a lollipop.

But I quickly realise these elaborate dishes are something I’d struggle to emulate at home.

Any thoughts of putting down the fork and seriously picking up the spatula are swiftly dispelled during a cookery class with White, of TV’s Hell’s Kitchen fame.

He urges novice chefs to relax, by downplaying potential hazards: “What is the worst you can do, over cook it or under cook it?”

As I miss the boiling water and accidentally tip my dry macaroni into a lobster sauce, his words echo in my ears while pupil and teacher lock eyes.

The maestro never loses poise, draining the soupy mixture from the uncooked pasta, but I feel the pitying glances of my classmates as I try to hide behind the stove.

At least I manage to painstakingly chop an onion, very, very finely, long after fellow students have finished.

“Perfection is lots of little things done well,” says White, but the three Michelin star-winning chef is also feeling a bit nervous.

He is cooking for a handful of exclusive diners this evening, and confesses to finding the prospect a little daunting, but also intimate and enjoyable. “You learn to dissolve your fears on the stove.”

The father-of-three says he enjoys nothing more than tending to his apple trees and being out in the countryside. He also loves life at sea, preferring the waves to the city.

I am in full agreement, as we meander along a fjord outside Stockholm. The boat weaves between small islands with log cabins painted cream, accessible only by water. Jet-skiers play in the wake as the vessel drifts languorously, extending large ripples from its side.

We’re soon on our way to St Petersburg, Russia’s ‘window on the West’, which lies on the Baltic’s eastern extremity. Postcard-perfect classical buildings and Venetian-style canals define this former imperial capital.

I visit Peterhof, the summer palace of Catherine the Great. It’s dripping with gaudy Baroque-style gold ornamentation and chandeliers – all recreations, as the original riches were plundered by Nazi troops during the second world war.

More than 100 rooms were destroyed, but so far only 25 have been restored.

Outside the building’s Gulf of Finland-facing facade is an extravagance matching that of its interior: fountains with two golden kneeling half-human, half-beast figures dominate formal gardens, filled with topiary and manicured lawns. They soak me with spray as I elbow through crowds of tourists for a view.

Our day of culture concludes with a ballet evening under the high, stuccoed ceilings of the Grand Palace. The prima ballerina in St Petersburg native Pyotr Tchaikovsky’s Swan Lake displays perfect timing during dizzyingly long pirouettes, losing herself in the dance.

On board Britannia, dancing isn’t quite of the same mesmerising quality. But the mostly middle-to-old-aged passengers happily waltz and shimmy into the small hours at the Crystal Room dancing lounge, as I relax with a drink.

The demographic is tactfully acknowledged by some of the services on offer, including spa treatments for puffy ankles and arthritis, and ship photographers promising soft-focus treatment for customers to make them appear 10 years younger.

Yet the buzzing social life on board would make many a 20-something wilt, and the vessel abounds with vigorous 60-year-olds in chinos and polo shirts, pullovers tied over shoulders.

Julian Smith, a soprano saxophonist who featured in the 2009 series of Britain’s Got Talent, plays Ennio Morricone’s soundtrack to 1986 film The Mission, as I stand at the back of a crowded auditorium, surrounded by passengers in their most elegant evening gowns and black tie outfits.

I then head to dinner in Sindhu, a low-lit and tastefully decorated part of the ship that could be a raja’s quarters. A chicken tikka pie in thick pastry combines UK staples with a wild berry compote, providing an original and zingy contrast.

A chocolate pudding with a perfectly molten centre follows, coupled with a blood orange sorbet.

Afterwards, I retire to the Crow’s Nest bar at the front of the ship, which has an impressive menu of London and Plymouth gins, and listen to the piano player.

My ambitions to be a gourmet chef may have quickly sunk without trace, but a holiday spent dining on fine food and even finer views has been nothing short of plain sailing.

Photo: www.pocruises.com