IT IS one of the most unusual vehicles ever to be built in Britain - and the 30 birthday of the Sinclair C5 is being marked at the National Motor Musuem.

The electric-powered tricycle was launched on January 10, 1985, and though it failed to catch the public imagination at the time it is now regarded as an icon of 1980s design and a pioneer of alternative-fuelled transport.

Masterminded by inventor and entrepreneur Sir Clive Sinclair, the C5 was designed to be an inexpensive alternative for one person to travelling by car, bus or bike.

Marketed as ‘a new power in personal transport,' it had a retail price of £399 and could be driven for five miles on just a penny's worth of electricity.

However, the C5 was poorly received by the press and public alike, not least because its size - just 2ft 7ins off the ground - made it vulnerable on the road.

The claimed range of 20 miles on one battery charge was modest due to the limitations in contemporary battery technology.

And even if the ‘weather cheater' poncho, offered as an accessory, was worn by the driver, the C5's lack of rain protection also ensured a short production life.

Although Sinclair had expected to sell up to 100,000 units per year, only 9,000 C5s had been built by October 1985, following the end of production and the collapse of the company that Sinclair had set up to produce it.

The C5 utilised both pedal power and an electric motor for propulsion, with the driver sitting exposed to the elements in the open plastic bodyshell.

Handlebars beneath the driver's knees provided controls for steering, braking and acceleration, and the design of the three-wheeled backbone chassis, constructed from steel, had been extensively developed by sports car brand Lotus.

An electric motor powered the left-hand rear wheel, helping the C5 to reach 15mph - its top speed, as restricted by law - and anyone over the age of 14 was permitted to drive one, though no driving licence was required.

Just a single button was pressed to make it move and though rumour had it that the C5 was powered by a washing machine motor, because it was built by Hoover in Mwrthyr, Wales, that wasn't actually the case.

Every model, however, was supplied to its new owners in a cardboard box.

By the time that the C5 was launched, Sinclair already had an impressive list of designs to his name - including the digital watch, the world's first slimline pocket calculator and the world's first pocket television.

The C5 can be seen as part of a visit to the whole Beaulieu attraction, which also includes Palace House, Beaulieu Abbey and World of Top Gear.