Snobbery is integral to boating. It is not just the sailing yachties who refer to those with motor boats as ''stinkies'' or the fact that those with lavatories on their boats call those owning a craft without a loo ''nettle-crouchers'' or even the absurd use of nautical jargon (the pointy end, for example, must be called the bow).

It is also that every boat owner is acutely aware of his or her vessel's standing in relation to its neighbour. And that is true whether you possess a superyacht, sail a racing boat or just mess about on the river.

On the River Thames, for example, the mahogany-planked Edwardian Gentleman's saloon day launch, the sort of vintage boat used by the judges at Henley's Royal Regatta, is considered a cut above the traditional Slipper boat with its sloping stern and split windscreen (and frequently driven by a chap in a petty officer's cap and blazer).

The Slipper owner, meanwhile, is contemptuous of that nautical low-life, the fibreglass gin palace.

All three, however, look up to a Dunkirk "Little Ship", one of the 100-plus vessels still in existence that helped evacuate our troops from France in 1940.

Today, nearly all the surviving Little Ships have metamorphosed into well-preserved pleasure craft, many of which will cross the Channel this month to celebrate the 70th anniversary of the evacuation from France.

The Gainsborough Trader, however, will not be among them. The 1931 steel-keeled barge, which arrived in Dunkirk on May 31 1940 and ferried troops from the beaches to the larger vessels, will stay in London hoping for the tread of a homebuyer's loafer rather than the nostalgic thud of a sailor's Wetboot.

For the 72ft barge is no longer a heroic cockleshell, but a three-bedroom metropolitan bolthole where the only privation is the lack of a privet hedge.

After the war, the Gainsborough Trader returned to her original trade as a Thames lighter (she still has her masts, sails and rigging) before ending her days moored in Chatham, Kent, waiting to be broken up.

But instead of going to the scrap yard she was bought by Jay Jones-Cooper, a 45-year-old former Royal engineer, and his wife Dawn.

The couple spent 15 years reinventing the craft. Jay rebuilt the Kelvin KR4 88hp diesel engine and created the wooden interior.

Dawn, formerly a fashionable hairdresser, became a welder and sorted out the exterior.

The boat's wheelhouse was turned into the kitchen/breakfast room (with a Rayburn) while downstairs is a dining room, master bedroom and bathroom with double sinks and a large bath.

There is also a two-berth guest cabin and an outside hatch to another cabin in the bow.

Furthermore, it has a residential licence from Southwark Council to moor permanently in South Dock Marina in Southwark, opposite Canary Wharf. The licence costs £600 a year plus £5,200 for a safe mooring where swipe cards are needed to enter.

It is, in other words, an urban pad (with 1,200sq ft of living space) that gently rocks and rolls on the water. Although that is not how its owner would describe it.

"It's more than a houseboat," Jay says. "It's a proper seaworthy and historic boat with an original and rare diesel engine that crossed the channel in 2005 in a flotilla of the Dunkirk 'Little Ships'."

And as such, of course, it should be deferred to by those haughty City types in their concrete high-rise "Gin Palace" apartments a stone's throw away across the river.

• The Gainsborough Trader is on sale at £329,950, Chesterton Humberts: 020 7357 7999, www.chestertonhumberts.com