The last time you booked a minicab, were you picked by up by a £117,500 Bentley Continental, or perhaps a £77,100 Maserati Quattroporte?

No?

Well, according to figures obtained by Clean Green Cars, you were unlucky.

In London there are two Quattroportes registered as minicabs and no less than 17 Bentley Continentals, three Maybach 62s (combined value: £900,000) and an Aston Martin DB7.

The owners are said to be exploiting a loophole in the congestion charging laws - private hire vehicles are exempt.

Transport for London (TFL) has no criteria for suitability apart from an MOT certificate, as proven by the eight Mercedes SL models registered as private hire vehicles, even though they have no backseat.

When we questioned TFL about the list of cars, their answer bordered on the surreal.

"Having looked through the list...there are a couple of vehicles which might seem surprising - e.g. Transit vans." said a member of staff.

Er, no.

A Transit is one of the least surprising vehicles on the list, considering that Ford markets a specific private hire version called Tourneo.

How could a Transit be more surprising than a Rolls Royce Phantom in the eyes of TFL?

A spokesperson went on to say: "The Public Carriage Office (PCO), in conjunction with the congestion charging unit, undertakes regular checks to verify that licensed vehicles are being used for the purposes for which they were licensed. If information were brought to light to suggest abuse of the system, Transport for London and the Public Carriage Office would investigate this fully."

May we suggest the following?

According to Glass's Guide, the car valuation experts, a Maybach costs £5 per mile in depreciation before you factor in fuel (around 10 mpg in central London) and servicing.

How exactly do you run a Maybach as a private hire car when a London taxi charges less than £3 per mile?

A minicab without a usable back seat might be considered a contradiction in terms. Apart from the Mercedes SL and the Aston Martin DB7, there are also such gems as a Jaguar XK and a BMW 6 Series.

In urban London, there appears to be a boom in luxury off-road cabs: there are now over 100 registered, including two Porsche Cayennes, six Mercedes MLs and a Nissan Patrol.

Why would a minicab operator choose a vehicle that is heavier, thirstier and more expensive than a conventional saloon with the same amount of space?

The odd Range Rover for a luxury hotel is believable, but six Toyota Land Cruisers?

Despite the self-evident absurdity, there appears to be no end in sight for the supercab.

It costs £82 for the application and inspection and £27 per year for the license.

All private hire vehicles over 12 months must pass an MOT every six months.

That compares to £8 per day for the congestion charge - but of course that figure is due to go up to £25 per day in 2008 for cars emitting over 225g/km of CO2.

Stand by for yet more Range Rovers, Jaguars and Rolls-Royces to be licensed as minicabs. Just don't count on one whisking you home at 2am after a big night out.

Model and number registered as private hire vehicles

Aston Martin DB7: 1
Bentley (all models): 31
BMW M5: 1
BMW X5: 18
Cadillac Escalade: 1
Jaguar XK: 1
Range Rover: 52
Maserati Quattroporte: 2
Maybach 62: 3
Rolls Royce Phantom: 8