It’s hard not to find the idea that the EU could be moving in to the old Tory Smith Square HQ quite amusing, considering the decided shift against Europe in the party during the last thirty years.

The Tories moved in to number 32 Smith Square back in 1958 – the year after the EU was founded – before moving round the corner onto Millbank earlier this year. It was the time of Macmillan, the chap the Tories brought in to sort out the messy legacy of Churchill and Eden. Macmillan, the chap who first attempted to get Britain into the then EEC after Eden singularly failed to take any interest in the new alliance, and Churchill – despite being one of the prime instigators of the idea of European integration – deliberately ignored the new developments. Macmillan, the man who tasked Edward Heath with the job of buttering up our European cousins – a task Heath kept up with dogged determination for more than a decade until he finally managed to usher us in to the union in 1973.

It’s still quite bizarre to think that it used to be the Tories who were the party of Europe. But it was only with the onset of the rebate dispute from 1979 – with Maggie taking the then fair enough position that Britain was contributing too much to the EEC’s coffers – that the Tory love affair with Europe began to sour. Even then, the party remained largely keen on membership right up until the late 1980s (the EEC after all – and unlike the UN or USA – gave Britain its full, official support during the Falklands war), when Maggie set out her stall opposing further integration. It’s been downhill ever since, the Tories seemingly having given up any hope of the EEC/EU returning to the relatively simple customs and trading union they always wanted it to be.

Labour, meanwhile, though now painted as rabidly pro-European by the majority of anti-EU types, were constantly opposed to membership throughout the first 25 years or more of the EEC’s existence – campaigning for a “no” vote in the 1975 referendum, for Britain to leave during the 1983 general election, and for the rejection of Maastricht in 1992.

The Tories’ shift to opposition to the EU is, for me, entirely understandable. Its seemingly ever-expanding powers and swelling budget, not to mention the various aspects of the EU which have stifled free trade over the years, have increasingly begun to make it look like everything conservatives dislike – big, protectionist government.

But why have Labour shifted towards supporting the EU, having been so massively opposed to it for so many years? The rest of the radical policy changes the party’s gone through during the last twenty years make perfect sense – they’ve increased Labour’s electoral viability. But support for the EU is – rightly or wrongly – an electoral liability in the UK.

If you take the usual line that the shift from old to New Labour was designed to bring the party closer in line with the thinking of the country at large, jettisoning unpolpular socialist rhetoric in the process, how to explain the shift to favouring the EU, when the EU is supposedly so unpopular with the public? It’s something I’ve never quite understood.