Greeted and escorted up the purple-carpeted staircase with its grandiose balustrade, the ambassador and his assistant were ushered into the foreign secretary’s office. There, beneath the ceiling-high windows looking out on to St James’s Park, and their lavish crimson curtains, the two Russians took their seats on the overstuffed red leather armchairs. Tea was brought in and set down on the polished mahogany table: strong and black, the way the Russians liked it. Yet it was to be the most awkward of meetings for both sides.

‘If you will allow me,’ the foreign secretary began, dipping her head slightly as she peered over her glasses at her guests, ‘I would like to come straight to the point.’

‘Please.’ The Russian ambassador gestured for her to continue.

‘On behalf of the British government I would like to offer my apologies. It seems that we were – how can I say it? – a little hasty in our conclusions earlier. We now believe that a transnational criminal organization is behind this viral outbreak, rather than the Russian government.’

The ambassador stirred his tea, and said nothing.

‘And therefore,’ she continued, ‘we will be withdrawing the measures we announced on Friday. I am relieved that we have been able to reach this point before they were put into effect.’ The foreign secretary smiled bravely and looked from one to the other before the ambassador eventually spoke.

‘It is indeed a great shame that your government has chosen to portray my country in this way. You should know that Russia has only peaceful intentions in this world. We tried to explain this to you after the unfortunate death of Alexander Litvinenko and again after the Skripals were poisoned in Salisbury by that leak from your own laboratories at Porton Down. And yet, again and again, the British government chooses this path of needless confrontation.’ The ambassador regarded his host with a mixture of sadness and condescension.

‘Well,’ the foreign secretary began, somewhat taken aback by this defiant riposte, ‘I can only say that we extend our sincerest regrets at the earlier misunderstanding. In fairness, I should point out that there are still worrying indications that one or more individuals in your country’s security agencies may have been in some way involved so—’ She stopped: the Russian ambassador already had his hand up, palm facing her.

‘I regret to inform you, Madame Secretary, that the time for such empty apologies has passed. The damage has now been done.’

‘Well, I was actually offering you our regrets, Mr Ambassador,’ the foreign secretary said. ‘The important thing now is that we move on and look to future relations between our two countries.’