Theresa May, the Prime Minister, wrote a letter to Donald Tusk, the President of the European Council, with formal notification of Britain’s withdrawal from the European Union under Article 50 of the Lisbon Treaty. If no agreement is made sooner, Britain would cease to be a member in two years. The other 27 member states had celebrated the 60th anniversary of the Treaty of Rome. Asked by the BBC if Mrs May would be the ‘elephant in the room’ at the shindig, Jean-Claude Juncker, the president of the European Commission, said: ‘She’s not an elephant.’ Douglas Carswell, the MP for Clacton, announced that he was leaving the UK Independence Party, in whose interest he had been re-elected at a by-election in 2014, but would be sitting as an independent and not applying for membership of the Conservative party.
Three people were killed and 50 injured by a car deliberately driven at them on the pavement of Westminster Bridge. The driver crashed it into the railings of Parliament in Bridge Street, then ran round to the open Carriage Gates in Parliament Square and stabbed to death PC Keith Palmer. Tobias Ellwood, a junior Foreign Office minister, tried to resuscitate the stricken policeman, in recognition of which he was appointed to the Privy Council. The murderer was shot dead by a policeman protecting Michael Fallon, the Defence Secretary. The whole attack took 82 seconds. Lest another attacker had got into the Houses of Parliament, the Commons was suspended and MPs were kept in the chamber, their offices and later Westminster Hall and Westminster Abbey while police checked hundreds of staff and visitors. The attacker turned out to be Khalid Masood, aged 52, born in Erith, Kent, as Adrian Russell Elms, but known as Adrian Ajao after his stepfather.