In September 2017, Sadiq Khan, the Mayor of London, gave more clarity to the issue, relieving Transport for London of any obligation imposed on it by the previous Mayor, Boris Johnson, to fund a cost overrun. It was noted that at the budgeted cost of £284.4 million, the cost-benefit ratio of the project was only 0.4, so funding a cost overrun now estimated at £73.4 million on top of the £49.2 million Transport for London were already contributing, would not give value for money. It stated that Transport for London's sunk expenditure on the project was £71.2 million, of which £15.5 million was for buying an additional train, which has been delivered and put into service.