Edinburgh trams: What went wrong?

The Edinburgh tram project is overdue and over budget. What caused these problems?

For the first time, the company originally appointed to undertake the work has spoken about what, in its view, went wrong.

A confidentiality agreement prevented it from doing so before.

Dr Jochen Keysberg of Bilfinger Berger spoke to BBC Scotland's David Miller.

Watch BBC Scotland Investigates: The Great Tram Disaster on Tuesday 11 October at 22:35 BST on BBC One Scotland.