Train operator First Great Western has installed Oyster readers from West Drayton and Greenford into Paddington to allow commuters to use Transport for London's pay-as-you-go ticketing system.

The move follows an agreement announced in May by London mayor Boris Johnson between TfL and First Great Western, which will see the extension of Oyster pay-as-you-go to all London stations.

Following in the footsteps of his predecessor Ken Livingstone, Johnson will pour further investment into Oyster technology.

"Transport for London is investing £40m in new Oyster equipment and I will shortly be meeting with the other train operating companies to urge them to get onboard and make Oyster available to all Londoners," said Johnson.

Livingstone had already offered £20m to train firms last year to help fund integration with the London smartcard scheme by the 2009 deadline.

But fewer than half of the 10 firms running train services into London are ready to offer smartcard ticketing to customers.

Current operators using Oyster are Chiltern, C2C, National Express East Anglia on their Hackney area services, and Southern between Clapham Junction and Watford Junction.