Has the Government's failure to buy new trains for Thameslink put the entire upgrade of the multi-billion pound route at risk?
The Government was supposed to sign a contract for the trains three years ago.
Today the National Audit Office condemned that delay, saying it could mean the vital improvements to the route delay wont be ready by the deadline of 2018.
Political Correspondent Simon Harris reports.
More top news
Services on major rail routes between London and south west England have been severely disrupted after a person was hit by a train.
The business executive, whose ruthless interviewing technique has won him many fans, is replacing Nick Hewer, who quit after a decade.
Recent opinion polls show Labour within striking distance of capturing the trophy seat of Finchley and Golders Green.