On 25 October 2007, the council approved the final business case. Approval was given on 22 December 2007 for TIE to sign contracts with CAF to supply vehicles and BBS (a consortium of Bilfinger Berger and Siemens) to design and construct the network. Contract negotiations finished in April 2008, and construction started in June 2008. By this stage the cost of the project was estimated at £521 million. Funding problems and political disputes led to the scaling back of the original plans. In April 2009, the council cancelled phase 1b, citing revenue shortfall created by the economic slowdown to save an estimated £75 million. The Granton extension was also cancelled.