They look like a mode of transport from another planet and seem to defy the laws of gravity. With two wheels side by side, commuters can zip along on the electric devices, upright, at 12mph.
The Segway, the ingenious electric "gyroscopic" self-balancing scooter which riders can accelerate by leaning forward and brake by leaning back, has attracted thousands of dedicated fans, won over by its green credentials, cheap running costs and the sheer fun of learning how to ride one.
Lawmakers around the world, originally suspicious of the curious-looking devices, are increasingly changing their minds about their safety. Already legal in most states in America, Segways are becoming welcome in Europe, with governments beginning to permit their use on public roads. They have been legalised on the streets of Germany and Italy, and the Dutch government recently changed its mind to allow Segway enthusiasts to feel the wind in their hair.
Segways have also been adopted by hundreds of police forces across the globe: the vehicles' speed and manoeuvrability mean officers can patrol three times as much ground as on foot.
Yet the Segway's popularity and lack of emissions have not impressed the British Government. It remains banned from British roads, pavements and parks, and is permitted only on private property. The Department for Transport (DfT) cites safety concerns, specifically about the device's brakes and the absence of lights.
Renewed political momentum is building, though, for the whacky racers to be legalised in this country. Both the Liberal Democrats and the Conservatives have lobbied the Government to allow the scooter's use along cycle paths. The DfT says that its objections have not yet been addressed, but that it is in discussions with the manufacturers about introducing safety measures.
The pro-Segway campaign will receive a welcome boost tomorrow when a group of MPs and peers lead an (illegal) whirring convoy of the transporters from the Houses of Parliament to the Department of Transport – a journey of about five minutes. Once the curious troupe of futuristic travellers reaches the front door of the DfT, its members will demand the launch of an investigation into whether the Segway could play a key role in unblocking Britain's gridlocked main roads.
The party, which includes the Conservative peers Earl Attlee and Earl Liverpool and the MPs Stephen Pound and Lembit Opik, will also ask the Government to set out a clear road map detailing how the Segway can be accepted for use on the streets.
With a top speed of just over 12mph – faster than the average speed of cars in central London – the scooter's supporters insist they could beat congestion in major cities. The Segways, which cost about £4,400, have a range of 24 miles and can be fully recharged in eight hours.
Stephen Pound, the Labour MP for Ealing North, has already forced fellow parliamentarians to witness his enthusiasm for the device. Several had to dive for cover as he test-drove one around the atrium of Westminster's Portcullis House, cackling as he wove in and out of the tables of alarmed MPs and advisers.
"I was demonstrating its manoeuvrability," he said. "I wanted to show they are so easy to drive that even an MP can do it. You just lean forward to speed up and back to slow down. It is a bit counter-intuitive at first, but anyone can soon get the hang of it."
Supporters argue that Segways should be treated the same as a powered push bike, which are permitted on the roads.
"The problem is the innate conservatism of Labour governments, which can be irritating at times," said Mr Pound. "There is no real reason that these wonderful bits of kit should be kept off our streets at a time when we are battling high fuel prices, congestion and climate change."
And if tomorrow's protests fail, the fight for the Segway could end up in the courts – if Mr Opik has anything to do with it, that is.
The eccentric Liberal Democrat MP says he is even prepared to go to prison for the Segway cause. "Legalise Segways or send me to Strangeways," he urged yesterday. Tempting fate.
He says he has been cruising illegally around his constituency in his Segway since receiving one last month, and will continue to do so as a protest against the Government's position, which he says is "completely unjustified".
"I'm prepared to go to prison over this – the Government just seems to be against them for the sake of being against them, and that just isn't good enough anymore," he said. "I'll ride it to my appearance at the Old Bailey if I need to."
The makers of the Segway claim that it is all but impossible to fall off one, but some high-profile mishaps have bruised their cause – and other's torsos. George Bush fell off his in Kennebunkport, Maine, in 2003. The President escaped the tumble unscathed.
Piers Morgan, though, was not so lucky. The former editor of the Daily Mirror broke five ribs and suffered a partially punctured lung when he took a dive while giving one a test run in California last year. The incident, which was caught on camera and remains a hit on YouTube, was made all the more embarrassing as his paper had previously mocked President Bush for his lack of Segway skills. "Since only President George Bush and I are known to have come off them, I suspect the manufacturers still believe they have the right to call them 'idiot proof', and your readers might agree with them," said Morgan yesterday.