A rumour I had heard before - but repeated as part of a keynote speech by a presenter  at yesterday's RailFuture meeting, and who's views and information I respect:

The Deparement for Transport hadn't budgeted for anything like the 1.3 billion that First Group bid for the franchise - it's some 300 million more that they  thought they would get. The Treasury is allowing the Department to keep the money which will be used to pay for overspends on road building programs.

In other words, a decent train service between Swindon and Westbury, which would cost 10 million pounds to run for 10 years, and 30 other such services, have been sacrifised by First in their keenness to win the bid, and the extra money that First will have to charge customers to make its payments to the government will in part go to the funding of overbudget / mismanaged road building programs.