London Mayor Sadiq Khan has ordered an investigation into the Olympic Stadium as the cost of converting it into West Ham's football ground has soared by £51million.
The modification of the London Stadium, as it's now known, was predicted to cost £272million but this has risen to £323million.
One of the main reasons behind the rise is that the annual cost for moving the retractable seats, which was estimated at £300,000, in fact amounts to £8million.
Several rows of seats have to be moved back at the end of the football season in May 2017 when the stadium will be used for athletics and concerts instead.