The UK will expel 23 Russian diplomats as part of a series of measures following the "attempted murder" against Sergei Skripal and his daughter Yulia, with Theresa May laying the blame for the attack at Russian President Putin's feet.
According to the Prime Minister, the diplomats have been identified as "undeclared intelligence agents." The expulsion represents the biggest expulsion of diplomats in over 30 years, which "reflects the fact that this is not the first time that the Russian State has acted against our country".
They have one week to get out.
May also confirmed that no ministers and no members of the Royal Family would attend the World Cup, which will take place in Russia this summer.
She added that the UK will suspend all high-level contacts with Russia. A planned visit from foreign minister Sergey Lavrov has been cancelled.
Checks on private flights, customs and freight will be increased and the government will freeze Russian state assets "wherever we have the evidence that they may be used to threaten the life or property of UK nationals or residents".
May added: "Led by the National Crime Agency, we will continue to bring all the capabilities of UK law enforcement to bear against serious criminals and corrupt elites. There is no place for these people – or their money - in our country."
On top of this government is "urgently" readying a new bill to harden our defences against all forms of hostile state activity, which will include "a targeted power to detain those suspected of hostile state activity at the UK border", May said. This power is currently only permitted in relation to those suspected of terrorism.
Home secretary Amber Rudd has been asked to consider whether there is a need for new counter-espionage powers to clamp down on "the full spectrum of hostile activities of foreign agents in our country".
The government will also table amendment to the Sanctions Bill in relation to the violation of human rights.
"In doing so, we will play our part in an international effort to punish those responsible for the sorts of abuses suffered by Sergey Magnitsky," May said. "This will command cross-party support."
On Monday the Prime Minister warned that if there was no "credible" explanation given by midnight yesterday, she would announce a series of retaliatory measures today.
This afternoon Theresa May said Russia had not done so, instead replying with "sarcasm, contempt and defiance".
She added: "There is no alternative conclusion other than that the Russian state was culpable for the attempted murder of Mr Skripal and his daughter - and for threatening the lives of other British citizens in Salisbury, including Detective Sergeant Nick Bailey."
May named the Russian President directly, saying while the UK had "no disagreement with the Russian people... it is tragic that President Putin has chosen to act in this way".
Labour leader Jeremy Corbyn drew cries of disbelief from MPs in the chamber as he asked the Prime Minister whether the UK had met its obligations under the Chemical Weapons Convention - repeating comments made by Lavrov yesterday.
Although he condemned the act, Corbyn made no direct condemnation of Russia or acknowledgement of the link - although several of his own MPs, including Yvette Cooper, later did.
The Russian Embassy has slammed the moves, particularly the decision to expel 23 diplomats, saying it was a "hostile action... totally unacceptable, unjustified and shortsighted".
It added: "All the responsibility for the deterioration of the Russia-UK relationship lies with the current political leadership of Britain."
Ahead of the Commons debate Nato issued a statement saying the act was a "clear breach of international norms and agreements".
It added: "Nato regards any use of chemical weapons as a threat to international peace and security."
The UK now has the support of a number of allies, including the EU as a whole and individual member states including France and Germany. Last night May spoke with Donald Trump, who told her the US "was with the UK all the way", and agreed the Russian government "must provide unambiguous answers as to how this nerve agent came to be used".