Britain will not be “cowed” by the threat of terrorism in its cities, the Prime Minister has said, following an attack on Parliament in which four people died.

In tributes in the House of Commons this morning Theresa May said the attacker, who has since been named as Khalid Masood, 52, “did not succeed” in getting past Parliament’s gates and that police did their job “heroically”.

“We know the threat from Islamist terrorism is very real. But while the public should remain utterly vigilant, they should not – and will not – be cowed by this threat,” the Prime Minister told MPs.

She said the act of terrorism had “tried to silence our democracy”, but pledged: “We are not afraid and our resolve will never waver in the face of terrorism”.

She continued: “The greatest response lies not in the words of politicians, but in the everyday actions of ordinary people. For beyond these walls today, in scenes repeated in towns and cities across the country, millions of people are going about their days and getting on with their lives”

Labour leader Jeremy Corbyn thanked public servants for their work respond to the attack, and in particular noted a Conservative MP who had gone beyond the call of duty.

“As the Prime Minister said, when dangerous and violent incidents take place, we all instinctively run away from them, for our own safety,” he said.

“The police and emergency services run towards them. We are grateful for the public service yesterday, today and every day that they pull on their uniforms to protect us all.

“I want to express our admiration to [Tobias Ellwood], whose efforts yesterday deserve special commendation. He used his skills to try to save life.”

Mr Corbyn also paid tribute to Keith Palmer, the police officer who was stabbed dead in the attack, and to the police and security services who “keep us safe every day” on the Parliamentary estate.

He also echoed similar sentiments to the Prime Minister, arguing that the UK must not allow “fear or the voices of hatred to divide or cower us”.

PC Palmer, the slain police officer served as a reservist from August 1987 to August 2001, leaving as a bombardier, and had 15 years of service in the police.

Conservative MP James Cleverly, who had met the Pc 25 years ago as part of Battery 100 Regiment, Royal Artillery, paid a tearful tribute to his late comrade.

“He was a strong, professional public servant and it was a delight to meet him again only a few months after being elected,” he said.

In pictures: Westminster attack Show all 9 1 /9 In pictures: Westminster attack In pictures: Westminster attack An air ambulance lands after gunfire sounds were heard close to the Palace of Westminster in London PA wire In pictures: Westminster attack MPs wait until the situation is under control in Westminster. 'The alleged assailant was shot by armed police,' David Lidington, leader of the House of Commons, told the house. BBC News In pictures: Westminster attack Crowds gather in Westminster after shooting incident, which police are treating as terror attack BBC News In pictures: Westminster attack Police were also called to an incident on Westminster Bridge nearby AP In pictures: Westminster attack Early reports indicate the car, which mounted the pavement on Westminster Bridge and mowed into around a dozen people, was the same vehicle which then rammed into the railings of the Palace of Westminster, just around the corner Reuters In pictures: Westminster attack Security sources described the suspected assailant as a middle-aged Asian man, who is understood to have left the car before attacking a police officer with a seven-to-eight inch knife PA wire In pictures: Westminster attack Police have asked people to avoid the immediate area to allow emergency services to deal with the ongoing incident AP In pictures: Westminster attack One woman has died and a number of others, including the police officer, have been hurt, according to a junior doctor at St Thomas' Hospital Reuters In pictures: Westminster attack At least three gun shots were heard by those inside Westminster, and proceedings in the House of Commons have been suspended AP

Four people including the suspected attacker and a police officer died in Wednesday’s attack. At least 40 others were injured in the attack, with seven reported to be in a critical condition.