She would be my prime suspect. A possessive, controlling harpy isn’t going to let her husband Eddie run off with another woman without putting up a fight first…” says flame-haired Angela Lucille, a secretary, who has just confessed undying love to her boss, Ivan Perseus, a spiv who’s done good, with a dubious war record. It’s just past midday on the British Pullman, a Belmond train and sister to the famous Venice Simplon-Orient-Express, and a Moving Murder Mystery is unfolding.

I arrive to Victoria at 10:30am and check in at the Belmond departure lounge, where 1950s songs are being crooned by a coiled-haired singer in a slinky dress on the platform. The advice is to dress up for the occasion and many of my fellow passengers have gone all out; the guys looking dapper in penny loafers, skinny ties, and pleated trousers and the ladies in voluminous skirts and fox furs. The day doesn’t come cheap, and most are here to celebrate special birthdays or anniversaries so there’s a real buzz of excitement as the Pullman arrives, and the actors hop out to peacock along the platform in extravagant ‘50s costume.

The brown and mustard-coloured Pullman is a raving beauty and stepping into one is a moment of bygone glamour. In 1972, the Cygnus carriage was featured in the film Agatha with Dustin Hoffman and Vanessa Redgrave and has always been a favourite with royalty and dignitaries (although, I’m told, that Nelson Mandela favoured carriage Vera with its springbok-designed marquetry). Two years ago, Cygnus was given an indulgent makeover by film director Wes Anderson (the refurbishment is rumoured to have cost a cool £2 million). Known for his expertise in creating the most exquisite of colour palettes, often with pastel pinks and greens, Cygnus is no exception with its candy-floss-coloured ceiling, and rich geometric-patterned upholstery in bottle green and lime tones. The mahogany wood panelled walls are a joy, decorated with waves, stars, clouds, and sunbeams, and settling down to enjoy a glass of champers in one of Anderson’s ample armchairs feels like the most indulgent treat.

The Cygnus carriage, renovated to a design by director Wes Anderson

Five hours on a train, however beautiful, might sound a little long but I’m soon so embroiled in the plot, delivered at regular intervals by a host of larger-than-life characters, that the hours, like the countryside we’re travelling through, flies by.“He wouldn’t last five minutes in fisty-cuffs with me, I can assure you,” bellows philanthropist Gordon Vera (an excitable chap with a curled moustache and bright green plus fours), while I’m tucking into my cannon of Kent lamb with potato and thyme cake.As the wine flows, the competition heats up between fellow passengers. It’s game on to discover clues and work out ‘whodunnit’, and there are those who are taking things quite seriously (full credit to the Russian lady sitting near me who whips a magnifying glass from her Chanel handbag). Masters of improv, the actors bat away every question or challenge thrown at them by us amateur detectives.

“Have you seen Jealous Eyes, my new film, darlings?” asks legendary actress, Julie Ibis.When someone quips back that he watched it on Netflix, she responds, “Oh darling. Isn’t that the wonderful new picture house in Clapham?”During a lull, I nip along the corridor to check out the tiny kitchen, from which fine-dining creations being whisked away by dashing, white-uniformed stewards, and, in between skits, there’s ample time to gaze out of the window. We pass fields of hops and vineyards, and in keeping with the surroundings, you’ll find a good selection of Kent’s finest wine on the Carriage Wine List, including a Simpsons Canterbury Rose. As we depart from Dover Priory Station, the British Channel laps just a pebble throw away from the tracks, and by the time we’re on the outskirts of London, we’re enjoying a ‘Great British cheeseboard’ and glorious views to The City. It’s as we’re crossing the River Thames back to Victoria that the identity of the murderer is revealed. Of course, I mustn’t divulge any secrets but can tell you I was wrong in my choice of villain. I might just leave you with one piece of advice: that no one is quite who they seem.

The Moving Murder Mystery experience aboard the British Pullman, A Belmond Train from £485 per person, to include champagne, immersive theatre experience, five-course lunch, sommelier's selection of wines, coffee, tea and petit fours. Visit Belmond.com.Want to make an indulgent night of it? Double rooms at The Cadogan, A Belmond Hotel is in Chelsea (20 minute walk to Victoria Station) start at £680 per night (based on two sharing).

Murder on the British Pullman