It was when Sergei Lavrov and his aides raised their eyes heavenwards and performed the sign of the cross in unison that I realised how almost anything was possible during a meeting with Russia’s minister of foreign affairs.

Instinctively, I glanced under the table, just in case the floor beneath the seats of the British delegation was slowly opening to reveal a tank full of sharks.

We were visiting the Russian mission at UN Headquarters in New York, and Boris Johnson, then foreign secretary, had just mentioned Alexander Litvinenko, the former spy who was horribly murdered with polonium poison by Russian agents in London.