The Commissioner said: "I have decided it is the right time for me to step down as London's Transport Commissioner.

"It has been a privilege to serve as London's first ever Commissioner for Transport.

"TfL has more than proved it can deliver since it was formed five years ago.

"I thank Ken Livingstone for the opportunity to start rebuilding this great city's transport network.

"Above all, I thank all the employees of Transport for London for their professionalism.

"I will never forget their commitment to London during the morning of July 7th and in the days and weeks that followed."