A ban on using two-wheeler Segways has deliberately been flouted by an MP in protest at the law.
Lib Dem Lembit Opik rode a Segway up and down outside the Houses of Parliament, challenging ministers to have him arrested.
He was joined by Conservative peers Lord Attlee and the Earl of Liverpool on the five-minute demonstration.
Both the Tories and Lib Dems have called for the 12mph battery-powered vehicles to be allowed in cycle lanes.
The Segway Personal Transporter, which can carry one person for 24 miles before it needs to be recharged, uses gyroscopes to maintain balance but can only be driven on private land in the UK.
It is illegal to use them on highways or pavements.
Mr Opik says it is very flexible, convenient in rural areas as well as large cities - and environmentally friendly.
The MP said he uses his Segway to travel about his Montgomeryshire constituency and has trained dozens of his constituents to use them.
"This is the biggest step forward in transportation since the Wright brothers," the MP joked as he showed off the machine to the media.
The MP had stencilled "Police" on the front of his Segway to "make a point" about how they could be used by the Metropolitan Police.
He claimed the devices would herald a transport "revolution" in the capital as commuters turned to them instead of cars and bicycles.
Asked by one reporter if it was appropriate for an MP to be promoting a commercial product in this way, he said: "Lighten up".
Earlier, the MP said: "It seems ludicrous that such an environmentally friendly way of getting around has been dismissed by the British government".
He said the government seemed "paralysed with indecision".
"On the one hand they say that the Segway PT isn't legal, on the other hand they are unable to point to a single scrap of evidence in British law to show why they should be banned."
He added: "For these reasons I've decided to take a stand, and am challenging the government to either have us arrested or to accept that not doing so means the Segway PT is effectively legal transport."
Mr Opik said they were already used by hundreds of police forces across the world and at Heathrow Airport. US President George Bush famously fell off one in 2003.
We would require robust evidence to support the benefits and further consideration of the risks posed to users and others before reviewing this policy
Dept for Transport spokesman
Some 250,000 have been sold worldwide. It is thought there are about 2,000 in the UK, where they cost around £4,300 each.
In its guidance, the Department for Transport says it would be "difficult" for scooters such as Segways to meet the standards required to be classified as road vehicles.
Segways and other scooters are not included in the same category as bicycles, as they cannot be pedalled.
A spokesman for the department said: "The safety of pedestrians, cyclists and motorists is our primary concern.
"The Segway does not currently meet basic safety standards for use on UK roads - for example an absence of lights and indicators, and the lack of a back-up braking system.
"Current legislation restricts Segway use in the UK to private land e.g. airports, shopping malls etc.
"We would require robust evidence to support the benefits and further consideration of the risks posed to users and others before reviewing this policy."
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