IS it the end of the line for HS2?

Yet another red flag is waved today - this time from those first class travellers, the Institute of Directors - which insists that if there is £50bn to spend, then better spend it on upgrading the west and east coast mainlines rather than David Cameron's "grand folly".

It was ex-Transport Secretary Alistair Darling - the man who likes to say no - who put a spoke in the Coalition wheel by exercising every politician's basic right: he changed his mind. The man who signed off HS2 when in office now believes pouring £50bn into a single project could well starve other elements of the rail network and turn it into a transport nightmare.

The former Chancellor's intervention, which followed a similar one by Lord Mandelson, led me to wonder if there was a deal of behind-the-scenes Labour co-ordination going on; the old outriders' technique. Within hours of Mr Darling's critique, Ed Balls, the Shadow Chancellor, miraculously popped up to insist Labour would "not sign a blank cheque" on HS2 and then Maria Eagle, the Shadow Transport Secretary, warned that another increase above £50bn and Labour would pull the cord.

One interesting aspect of the IoD's survey is that most of its members believe the place that will benefit from HS2 most is London.

The grand plan is to start work in 2017 on a new line from the Big Smoke to Birmingham and complete it within 10 years, with a further stretch to Manchester and Leeds up and running by 2033. The first stretch alone would, insists the Coalition, create 40,000 jobs.

With trains zipping along at 250mph, the London to Birmingham trip would be cut to just 49 minutes, from 1hr 24mins, and the London to Manchester journey halved to just over one hour.

Of course, any extension to Scotland is not on the map but building the high-speed line in England would cut journey times between Glasgow/Edinburgh and London by an hour to three hours 30 minutes.

Nick Clegg, who represents a Sheffield seat, has argued HS2 would help heal the north-south divide; it would certainly have an impact on property prices. But the most vociferous HS2 proponent has been Labour's Lord Adonis, the former Transport Secretary, who urged his colleagues not to give in to the siren voices, which would be, he said, "an act of national self-mutilation".

He warned Ed Miliband not to repeat the mistakes of a previous Labour government, which 40 years ago cancelled the Channel Tunnel.

Indeed, given that much of modern life is driven by the need for speed, one has to ask if Britain is prepared to continue to be the slow man of Europe; France's TGV travels at 200mph, Thalys in Germany 186mph, while the UK's Inter-City engines trundle along at 125mph.

And yet on the continent many countries have publicly owned railways. With British train-users paying the highest prices in Europe, if the Labour leader is looking for a distinctive, clear red-water policy - which he is - then he might look to scrapping the private franchises and handing the railways back to the taxpayer. It would certainly grab the headlines; it might even win Labour a few votes.