Microsoft is currently running a somewhat unusual promotion for its Office 2007 suite - it's offering Londoners a free taxi ride in any cab bearing Office advertising.

Some 20 London black taxis have been covered in Microsoft Office 2007 advertising, and are available for anyone to hail. On weekdays between 7.30 and 9.30am all rides in the special cabs within zones 1 and 2 in central London are free, courtesy of Microsoft.

Passengers taking the free rides will also get a postcard offering a free trial of the software.

"As the weather gets hotter and the tube more unbearable, we are helping London's workers have a better day by laying on free cabs to keep them fresh in body and mind," said Darren Strange, UK product manager for Microsoft Office 2007.

"Office 2007 is all about helping workers do their job better and, by allowing them to get a free taxi to work, we hope this will help them too."

The free taxis will be in circulation in the Capital until 8 May.