A London-based Dutch lawyer became the first person jailed as part of the investigation into whether Donald Trump’s campaign colluded with Russia during the 2016 US presidential election.
Alex van der Zwaan, 33, the son-in-law of one of Russia’s richest men, was sentenced to 30 days in jail and a $20,000 fine at a court in Washington.
His connection to the inquiry led by special counsel Robert Mueller was tangential, and Van der Zwaan will go down as a footnote in history.
But Michael Zeldin, a lawyer who once worked for Mr Mueller, said: "This sends a message that Mueller is serious about people co-operating."
Van der Zwaan had previously pleaded guilty to lying about his contacts with former Trump campaign aide Rick Gates, and a former Russian intelligence official referred to as "Person A".
The FBI has alleged that in 2016 Van der Zwaan and Gates were both in contact with "Person A" who they knew to be a former official of Russia’s GRU intelligence agency.
Van der Zwaan lied to investigators about it but then began cooperating, which led to a lighter sentence.
In court documents Mr Mueller’s team said Van der Zwaan was "in an unusual position of having information related to the investigation that is not widely known".
Van der Zwaan lives in London and is married to the daughter of Russian billionaire German Khan, founder of Alfa Bank.
The convicted lawyer told the court: "What I did was wrong. I apologise to this court, and I apologise to my wife."
US District Judge Amy Berman Jackson said it was necessary to jail him to deter others from lying to investigators.
It also emerged that Rod Rosenstein, the US deputy attorney general who appointed Mr Mueller, had explicitly authorised him to investigate allegations that Paul Manafort, Mr Trump’s former campaign chairman, colluded with the Russian government.
According to a court document filed by Mr Mueller’s team, Mr Rosenstein wrote a memo giving the authorisation in August.