The Ukrainian ambassador to the UK has received a rare standing ovation from MPs in moving scenes at the start of Prime Minister's Questions.
Commons Speaker Sir Lindsay Hoyle confirmed that Vadym Prystaiko was seated in the gallery above the chamber to watch the weekly clash.
MPs, officials and journalists stood up to applaud for nearly a minute in a show of solidarity with the Ukrainian people in the face of Russian aggression.
Sir Lindsay told the top diplomat: "We generally do not allow applause in this chamber but on this occasion the House quite rightly wants to demonstrate our respect and support for your country."
Some politicians wore the blue and yellow of the Ukrainian flag, including ex-PM Theresa May, SNP MP Alison Thewliss and senior Conservative MP Bill Cash.
Mr Prystaiko, who was flanked by Deputy Speaker Dame Eleanor Laing and Tory MP John Lamont, nodded in gratitude as MPs applauded.
Boris Johnson told MPs that “Putin has greatly miscalculated” with his brutal onslaught in Ukraine, adding: “He has underestimated the fortitude of the Ukrainian people and the unity of the free world in standing up to his barbarism.”
He said the Western would would “join us in condemning Russia and demanding Putin turn his tanks around.”
“If Putin doubles down, so shall we”, the Prime Minister added - including sending finance, weapons and humanitarian assistance to the Ukrainian government.
Mr Johnson explicitly said for the first time that Vladimir Putin was waging war crimes in Ukraine.
SNP MP Ian Blackford said: "Vladimir Putin is a war criminal. And one day soon, Putin must face justice in the Hague.
"To prosecute Putin and his regime, the full range of war crime charges must be used including the crime of aggression by a state. Will the PM amend the UK’s war crimes act and will he support the ICC prosecution for Putin’s crimes of aggression?
Mr Johnson replied: "I can tell him that what we have seen already from Putin’s regime. In the use of munitions they’ve been dropping on innocent civilians in my view already qualifies as a war crime and I know the ICC prosecutor is already investigating."
Labour leader Keir Starmer pressed the PM to tighten the sanctions regime against Russia as he demanded to know "why on earth" Chelsea FC owner Roman Abramovich is not facing sanctions as he had a "public association with corrupt activity and practices".
Mr Johnson replied "it’s not appropriate for me to comment on individual cases at this stage".
But he added: ""But what I can say and I stand by what I've said in the House and what we put on the record, but be there no doubt that the actions that we've already taken, that this House has already taken, are having an effect in Moscow, and by exposing the ownership of properties, of companies in the way that we are, by sanctioning 275 individuals already, a further 100 last week, that the impact is being felt."
