Sergei Skripalt old friends Vladimir Putin would ‘get him’

He said that, prior to giving evidence at the inquiry, he had checked with those friends, asking them “he did say that, didn’t he?” and they had confirmed it.

Mr Cassidy told the inquiry that he and his wife had later googled Mr Skripal and discovered his spying activities.

He also said that on the way home from picking Mr Skripal’s daughter up from Heathrow Airport with him – the day before they poisoned – he believed he was followed by an undercover police car.

Mr Cassidy said he first passed what he believed to be a white unmarked police car and slowed down as he was over the speed limit and then noticed the black BMW keeping pace, either in front or behind him, “for a really long distance”.

He told the inquiry: “Because of what happened the following day, I put two and two together and came up with some conclusion that we were probably being followed.”

Later, Commander Dominic Murphy, head of the Metropolitan Police’s Counter Terrorism Command, told the inquiry that the two vehicles had been identified as Hampshire Police patrols.

He added he was satisfied that they were engaged in “entirely unconnected” police matters at the time.

The inquiry, chaired by former Supreme Court judge Lord Hughes of Ombersley, opened at the Guildhall in Salisbury earlier this month but started hearing evidence in London on Monday.