The HS2 debate continues to gather a considerable head of steam following a troubling few weeks for the ‘UK’s largest infrastructure project.’

A supply chain conference is to be held in Birmingham at the ICC on Bonfire Night, to which apparently more than 500 businesses have ‘registered an interest’ in winning more than £10 billion of contracts.

One of HS2’s advocates in chief, Jerry Blackett, Chief Executive of the recently renamed Greater Birmingham Chambers of Commerce, says businesses are ‘taking the right approach towards the procurement opportunities of HS2.’

As well they might if the £10 billion worth of contracts on the table is an accurate figure. But one of the problems of the HS2 debate is that the sums seem to be as reliable as the notorious London Midland rail service of a few months ago.

The Government has already officially increased the cost of the project by nearly £10 billion to £42.6 billion because of a ‘contingency fund to cover the cost of potential problems with the programme.’

But if Boris Johnson is to be believed, the final cost will be £70 billion and upwards. Bozzer says £1 billion will have been spent by 2015 on consultation and litigation and the like without a single sod of turf being disturbed.

Other prominent critics of HS2 include former New Labour architect Lord Mandelson, who has described the initial costings as “almost entirely speculative” when Gordon Brown’s Cabinet backed the idea.

Former Chancellor Alistair Darling has joined the ranks of critics, Public Accounts Committee chairman Margaret Hodge says the case for HS2 is ‘spurious,’ rebel Tory Bill Cash calls it a ‘Whitehall elephant’ and so on and so forth.

It would only be fair to Jerry Blackett and the supporters of High Speed Rail to point out that being lectured on spending by the political classes in the knowledge of some of our MPs’ cavalier approach to expenses (think bath plugs, duckhouses, flipping and the like) is akin to the old joke about King Herod and baby-sitting.

But it’s not so much an argument about costs as about who picks up the bill. If the likes of Richard Branson, say, were to chip in with a few of his billions rather than the already over-burdened taxpayer, maybe we’d all feel a lot happier about HS2.