Liam Fox was in favour of a customs union with the EU before he was against it – his speech today was sabotaged by his own former opinions

Liam Fox was emphatic in his speech in the City of London today that a customs union “would be a complete sell-out of Britain’s national interests”. You might expect the secretary of state for negotiating trade treaties to be against a deal that would prevent the UK negotiating its own trade treaties.

It was not always thus. Six years ago, Fox was a backbench MP campaigning for Britain to leave the EU, having resigned as Defence Secretary for allowing his personal friend Adam Werritty to become involved in official government business.

Fox wrote an article for the Mail on Sunday in September 2012 setting out his vision for Brexit: he thought the “best way forward” would be an economic partnership “involving a customs union and a single market in goods and services”.

This would take our relationship with the EU back to the original idea of a free-trade area that we thought we were joining in 1973: “This would be, in effect, a common market without the political interference that the British people have found it increasingly difficult to tolerate.”

That article is still on Fox’s website, although its author is now of the opposite opinion. Fox’s problem is that his view in 2012 makes more sense than his view now. Even Jeremy Corbyn, his fellow-Eurosceptic, has realised that copying the EU customs union is the “best way forward”.

It would seem the Cabinet Brexiteers have decided to respond to Corbyn’s shift of policy by hardening their position. Boris Johnson, the Foreign Secretary, said: “Corbyn’s Brexit plan would leave the UK a colony of the EU.” Fox, in his speech today, called Labour policy “incoherent, inept and clueless”. He said: “As rule takers, without any say in how the rules were made, we would be in a worse position than we are today.”

It is not obvious this is wise, because it may not be possible to hold the line in Parliament. There is a majority in the House of Commons in favour of a customs union, which means the Government is likely to lose the vote when it comes.

Fox could not have expected, of course, that his speech would be sabotaged before he had even got to the lectern at Bloomberg’s new London headquarters by the person who was his top civil servant less than a year ago.

Martin Donnelly, who was permanent secretary of the International Trade department until last March, told Politico: “For the UK to give up existing access both to the EU single market, and to the preferential trade agreements which the EU has in place with over 50 countries, in exchange for its own bilateral trade deals at some future date, is rather like rejecting a three-course meal now in favour of the promise of a packet of crisps later.”

This is not the curtain-raiser you want for your turn in the limelight, as a cabinet minister delivering the fifth of six big speeches on Brexit, with just the Prime Minister’s speech on Friday to come. (Although Philip Hammond, the Chancellor, has been added to the bill with a seventh speech next week.)

But even more embarrassing is to have your own words quoted back at you. No wonder Fox arrived late and looked stern today. The Government’s push to sell its Brexit proposals – you know, the ones rejected by Donald Tusk, president of the EU Council, as “pure illusion” – is going rather badly. And it is mostly being undermined from within.