Downing Street said yesterday it was down to protocol that Mr Cameron would not meet the French socialist leader Francois Hollande during his visit to London today. That explanation could mean anything and it is more relevant to know that the British embassy in Paris had already advised M. Hollande that the prime minister would not be available to meet him during his visit to campaign for the votes of thousands of French expatriates living in London. In normal circumstances Mr Cameron would be right to avoid giving the impression of interfering in another country's election. But he has already done just that by expressing publicly his warm support for Nicholas Sarkozy's re-election as president when they were together some days ago and then by underlining his view with an interview in Le Figaro in which he described M. Sarkozy as a brave politician with great leadership qualities. Both interventions were unwise but could have been balanced by inviting Francois Hollande to a brief courtesy meeting at, say, the House of Commons. The fact that M. Hollande, who calls himself a social democrat, has a sizeable lead over M. Sarkozy in opinion polls at this early stage of the presidential election should not influence British political reactions to him but it is odd that someone who could become a close European Union colleague is not even entitled to a handshake.