Slowly but surely, David Cameron has moved in a Eurosceptic direction. From not wanting the Conservatives to talk about Europe at all, he has conceded a great deal. First he agreed with his backbenchers that there should be a referendum on Europe and then that that referendum be on the central question of Britain’s fundamental membership. He has since supported efforts to get a referendum bill on the statute book and has replaced a Foreign Secretary who wanted Britain to stay in the EU with one who is prepared to see Britain leave.

This morning’s Times reports (£) that he’s on the brink of another step: he’s ready to say that if negotiations fail he won’t recommend that Britain stay in the EU. It is an essential step for him to take. As The Times argues in its leader column (£), EU leaders are more likely to negotiate seriously if they believe Britain’s membership really is at stake: “The more explicit he is about the risks of failure… the greater will be his chances of success”.

This threat to leave the EU was almost made after Jean-Claude Juncker was installed as incoming president of the European Commission against the wishes of all of Britain’s political leaders. The PM decided against declaring his position then for fear of looking petulant. Mr Cameron will make it clear at an early opportunity, however, that although he intends to succeed in renegotiating Britain’s relationship with the EU he is prepared to countenance Brexit and every EU leader should recognise what is at stake. There is some suggestion that the announcement will be made at next month’s Tory Conference. That would be a shame as it would likely overshadow what should be a focus on a broader Tory offering to blue collar, northern and aspirational voters. The Conservatives should not use their last conference before the general election to talk about Europe.

David Cameron’s position would be more credible if his journey had appeared to have been voluntary. Instead it often looks like he has been dragged to it by his own backbenchers and by the threat of UKIP. Eurosceptics and supporters of Brexit, in particular, will nonetheless celebrate what they see as a tide of opinion running strongly in their favour. I’m not so optimistic about Britain freeing itself from rule-by-Brussels and I write that as a five-year-old Outer.

The opinion polls suggest that Brexit has only a very narrow lead in opinion polls or no lead at all. That’s not a good position to be in. The business community (including global companies) which supported Euro membership has yet to throw its resources in support of continuing membership. Outers will be subject to vilification and scare stories. Some limited form of renegotiation will be presented as a big deal. Then there is the swing to the status quo that characterises most referenda as “don’t knows” break for the known over the unknown.

Supporters of “Brexit” need to do a lot more to convince people that Britain can flourish as a more independent state – not cut adrift from the EU, as Europhiles suggest, but as part of a free trade arrangement with the EU. One of the lessons of the Scottish referendum campaign is that Alex Salmond was too sketchy about how an independent Scotland would flourish – particularly with regard to the status of the currency. The Outers must be able to clearly and convincingly describe how Britain would survive once the sovereignty of its parliament and courts had been restored.