With the government now being forced to make spending cuts, it would be an opportune moment to abandon the Inter City Express project. The arguments against it have been presented so many times that this is not the place to repeat them. From the moment the project was first mooted, Modern Railway has been publishing very well informed articles by Roger Ford, and writing from a different perspective, Ian Walmsley. According to various estimates, it costs between two and four times what it should and involves the premature scrapping of rolling stock with a decade or two of useful service life ahead. There is nothing I can usefully add.
The other project that needs to be subject to scrutiny is Crossrail. I commented on this before here. The main underground sections from Paddington to Stratford and Woolwich could be constructed as tube lines and integrated into the London Underground system, possibly taking over the Hammersmith and City branch of the Metropolitan Line. This should be significantly cheaper and would probably be more useful into the bargain.