The phoney war is over – the real campaign starts today.

The anti-HS2 forces have launched some penetrating early sorties, sounding like they know the numbers inside out and having come up with a number of plausible-sounding examples to back up their case that the economic case for high-speed rail is badly flawed.

Too often those in favour have fallen back, when pressed, on the line that HS2 will boost capacity on existing routes – but this is neither inspiring, nor does it sound like something worth spending billions on at a time of austerity.

Since the environmental benefits are indirect at best, the industry must be prepared to speak in more detail about the economic case for HS2 over the coming five months if it does not want to get out-manoeuvred in the media.

The time savings on the initial London-Birmingham route must be clarified – it was not reassuring to hear the anti-HS2 speak on the radio this morning in precise terms (“11 minutes”) while those arguing in favour were optimistic but vague (“at least half an hour”). The exact figures are of course hard to know at this point, but more clarity is needed than we have been getting so far.

This is set to be a huge consultation, with around half of people undecided. The ‘no’ campaign is larger, better-informed and more powerful than most HS2 backers expected – it will be a hard fight to recruit those undecideds into one camp or the other.