Alan Watkins: Mr Cameron's plausibility stops at Dover

The Conservative leader is vulnerable on foreign policy and defence, but he won't let that come between him and No 1

Considering his wealth of inexperience, we may wonder at Mr David Cameron's sure-footedness as Leader of the Opposition. Having Mr Gordon Brown against him certainly helps matters along. And, on the whole, he has been lucky. Sometimes, however, a row will blow up out of nowhere. The fuss about grammar schools was a case in point.

Everyone has now forgotten the row. It was not specially important even at the time. There were few such schools left in the country. The Tories had no plan to reintroduce the 11-plus. But the party's educational spokesman, or one of them, made a speech which was thought to be doctrinally unsound because it was unfriendly to grammar schools.

For a time, indeed, Mr Cameron's leadership was considered to be under a threat. The main reason was that Mr Brown was high in the opinion polls – or higher than he is today. It was not Mr Cameron's fault.

But other mistakes can certainly be laid at Mr Cameron's door. He appears highly vulnerable in matters of foreign policy and defence. It was only a few months ago when Mr Cameron was calling for the admission of Georgia to Nato, a development that might have brought about a war which would make the conflict in Afghanistan look like a local difficulty.

On Afghanistan, I am waiting for the Government's change of front. It may happen under Mr Brown or under his successor as a Labour prime minister. Neville Chamberlain and Anthony Eden both fell because of foreign policy. Tony Blair had to resign principally because of his support of Israel in the Lebanon.

Mr Brown might be thrown out by his party because of his stubborn support for the war in Afghanistan, started by Mr Blair, but supported throughout by Mr Brown. And where would Mr Cameron be then, obediently following Mr Brown? I am not saying Labour would win again on a cry of bringing the boys home from a savage land. But ending the war, if necessary under a new Labour prime minister, would almost certainly dent any Tory majority.

It is, however, on Europe that Mr Cameron has been most prone to make his mistakes. It is extraordinary that he took the Conservative Party out of its wholly respectable centre-right grouping, representing the present leaders of France and Germany – unaptly name the People's Party – and joined instead a collection of oddballs from Central and Eastern Europe.

I have heard it suggested that a previous leader, Mr William Hague, was influential in the change. Mr Hague has a certain hold of the party, particularly among its more elderly members. This is partly because they feel guilty about him, as they feel likewise, though not quite as strongly, about Mr Iain Duncan Smith (though not about Mr Michael Howard). It is also because Mr Hague represents the activists' feelings as Mr Cameron does not. Mr John Prescott was thought to perform the same function for Mr Blair.

We must try to be fair to Mr Cameron. He is not a model European constructed on the lines of the liberal press. He is, in the correct sense of that ugly and unnecessary word, a Eurosceptic, as distinct from someone who wants to come out of Europe completely.

I had always assumed that Mr Hague's true position was that he wanted to get out. Not so: or not, apparently, so. In last week's row about the Lisbon treaty, Mr Hague admitted that, in any conflict between European and

United Kingdom law, European law would prevail. This is what the European Communities Act 1972 says, and what several cases – in particular, one involving the Merchant Shipping Act and Spanish fishermen – have established since.

Mr Hague and Mr Cameron have talked about having a new human rights act and about safeguarding the sovereignty of Parliament. Mr Hague has referred learnedly, even if vaguely, to the German constitution, which protects German laws from European depredations. As I understand is the position, Germany has a federal constitution. It may not help very much.

This farrago of backtracking, obfuscation and sheer ignorance on the part of the Tories derives from an article by Mr Cameron in The Sun newspaper. It was in 2007, and gave a cast-iron guarantee to have a referendum on the Lisbon treaty. I went into referendum-mania last week in relation to Mr Blair's now happily unfulfilled European ambitions. It was largely a matter of positioning: between parties, between leaders and between Mr Murdoch and those who were anxious to secure his favour. For the past decade, all sorts of promises were given. No referendum was ever held. Arguably, this was a good thing. Mr Cameron has now joined the throng.

But it was clearly within Mr Cameron's contemplation that there would be a change of government in 2010. It was entirely within the bounds of possibility that all the countries would have ratified the treaty in 2009, as has happened already, even if there was a certain sleight of hand on the part of a few states.

There was nothing to prevent Mr Cameron, as the incoming prime minister, from having a referendum on the Lisbon treaty irrespective of whether the others had signed up. It would make things jolly awkward all round: that is all. Inevitably, the referendum would turn into a vote, not about the provisions of any treaty, but about whether we wanted to be in or out of Europe.

I remember the row about the referendum of 1975. The originator was Tony Benn. Edward Heath was prime minister, and Roy Jenkins resigned as deputy leader of the Labour Party on account of the referendum. Heath had already taken us into Europe on 1 January 1973, but Harold Wilson unexpectedly won the election which Heath foolishly called in 1974. Wilson, aided by his foreign secretary, James Callaghan, called for a renegotiation of the terms that Heath had already secured: much as Mr Cameron and Mr Hague are now calling for a renegotiation of God-knows-what terms on which we are currently in Europe.

The renegotiation of 1974-75 had been largely factitious. Wilson had pretended to be hostile to Europe, but really wanted to stay in all the time. He played no active part in the referendum campaign, but had an "agreement to differ" among the members of the cabinet, who, however, sided predominantly with Europe. So did the majority – 64.5 per cent – of the population of the United Kingdom.

For the rest of the 1970s, the Labour Party became increasingly suspicious of what was still called the Common Market. The party went on to fight the first two elections of the 1980s on a policy of coming out of Europe without a referendum of any kind. Towards the end of that decade, both parties reversed their positions. The turning-point was the address of the president of the European Commission, Mr Jacques Delors, to the TUC.

Just as the brothers from the branches became aware of the cornucopia of good things available across the Channel, so did it dawn on Margaret Thatcher that Europe was the source of political tyranny, strange ways and funny smells. With the poll tax, it brought down Mrs Thatcher. It helped to finish off John Major, William Hague and Iain Duncan Smith. Mr Cameron has no intention of going the same way.