We are back in the world of the Edwardian country house party. Not since the decade before the First World War have leading members of opposing parties socialised both with each other and with the rich and the powerful, like the Corfu taverna and yacht set did this summer. A century ago it was Asquith, the Liberal Prime Minister, and Balfour, the opposition leader – though a Rothschild was also often there, or acting as host.

Even though politics was very bitter then, there were cross-party friendships. Winston Churchill, then a Liberal, was hated by many Tories – his former, and future, party – but dined often with F. E. Smith, one of the most partisan Conservatives.

Of course, politicians now talk to each other at formal occasions, and the Prime Minister briefs other party leaders on security matters. But, otherwise, links are limited. Gordon Brown has practically no contact with David Cameron or Nick Clegg. None would dream of meeting up on holiday or over a weekend.

The rise of Labour and the class-based divisions of most of the 20th century ruled out close contacts across parties. The big exception was foreign trips by parliamentary groups. But friendships formed there seldom strayed outside Westminster.

Labour politicians often mixed with wealthy supporters, and donors. But such contacts were on strictly party lines. Harold Wilson had his collection of rich friends, some with rather dubious backgrounds, but they were generally all in the Labour camp. Similarly, Margaret Thatcher’s business friends were all Tories. Of course, there have been exceptions: Hugh Gaitskell and Roy Jenkins both had a taste for the grand social life, and had affairs with aristocratic women; while, on the Left, Michael Foot enjoyed the hospitality of the socialist-hating press baron Lord Beaverbrook.

Lines were blurred under new Labour: Tony Blair attracted support, and money, from people who would never before have backed the party, such as Bernie Ecclestone, as well as some involved in the loans-for-peerages affair.

Yet this did not stretch to socialising across party lines. For all Mr Blair’s “big tent” politics, liking for the wealthy, and holidays with celebrities such as Sir Cliff Richard, this did not include members of other parties.

The blurring of ideological lines has meant more social mixing among younger politicians, who often knew each other at university. But these contacts are seldom deep. The media provide a new link – journalists often retain long friendships across party lines.

But the Mandelson-Osborne meetings in Corfu are an exotic exception. Most current politicians are tribal: in their holidays as much as in their friendships and views.

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