At last, opposition to the HS2 rail project is extending beyond the Chilterns and is starting a debate that should have been had three years ago.

There has always been something deeply worrying about the fact that all three main political parties are in support of the plan to build a high speed railway line linking London with Birmingham, Manchester and Leeds when the case is so weak and the cost so high. The parties have been outdoing each other in attempts to show that their support is unyielding in the face of growing evidence that the whole project is unsustainable.

But outside Parliament, informed opposition is growing. The National Audit Office is querying the figures, the New Economics Foundation has produced a list of better uses for £33bn (it was before the recent cost rise announcement which now suggests £50bn including rolling stock) and on the Right several think tanks are questioning the case for the line.

As the line's supporters have become more desperate, they have been clutching at straws to justify the ever mounting cost of this massive project. First it was to speed up journey times and to improve the environment, then to boost capacity, then to bridge the north south divide and finally to create jobs and `agglomeration benefits'. But none of these stack up.

Wolmar is an internationally renowned expert on rail. He is also angling to be Labour's next candidate for Mayor of London.

And I still think that the best bet for a high speed line north is to rebuild the Great Central. It just doesn't go near key marginal constituencies which need to be flattered

keep to the Fen Causeway