Political editor Annabelle Dickson was in the House of Commons for Prime Minister's Questions, she described the scene as the drama unfolded.

EDP Political Editor Annabelle Dickson speaking live from the House of Commons

She said: 'A loud bang just before 3pm saw people run to the windows. There was a sense of foreboding that the moment people feared – an attack in or around parliament – had happened.

'The loud bang (people were unsure if it was the car or gun shots) meant there were fears a gunman might still on the lose.

'Police were taking no precautions and dozens of machine-gun weilding police swarmed into New Palace Yard.

MORE: Police officer stabbed and alleged assailant shot dead by police at Houses of Parliament

Political Editor Annabelle Dickson from Parliament

'Staff were told to stay in their offices and lock their doors. Those of us in the press gallery were also unable to move. MPs were locked in the House of Commons chamber as they waited for more information.

'Anyone wadnering around the parliamentary estate was escorted to safety.

'On the ground in New Palace Yard a man was being treated – the circumstances of his injury unclear. An attacker or the attacked it was hard to know.'

MORE: Norwich MP describes moment he was told police officer stabbed, assailant shot and people mown down outside Houses of Parliament

North Norfolk News: Emergency services close to the Palace of Westminster, London, after sounds similar to gunfire have been heard close to the Palace of Westminster. A man with a knife has been seen within the confines of the Palace, eyewitnesses said. Picture: Yui Mok/PA WireEmergency services close to the Palace of Westminster, London, after sounds similar to gunfire have been heard close to the Palace of Westminster. A man with a knife has been seen within the confines of the Palace, eyewitnesses said. Picture: Yui Mok/PA Wire

She said an ambulance arrived fairly promptly and an air ambulance was on the scene – a sign of how serious things were.

'But it was clear that it was not just in parliament that there had been an attack,' she said.

'The indications were that outside parliament something awful had happened.

'Over the road from Westminster station there was the wreckage of a car. Rumours of casualties on the bridge.

'Traffic was at a standstill until it was evacuated from Parliament Square 20 minutes or so after the first bangs were heard.

'Police are trying to piece together what has happen, but for now there is that dread that lives have been lost on what started as a routine Wednesday afternoon.

'As I leave Westminster late at night a policeman or woman at Carriage Gates will cheerily bid me farewell. In the morning I will be greeted with a smile.

'At the height of the summer they delight tourists posing for photos with a Big Ben backdrop.

'The children of one friend visiting from the US were delighted to be given a special welcome by a man with a gun.

'But the real reason our boys and girls in blue stand guard at Carriage Gates is to keep the thousands of people who use our historic parliament each week safe.

'They come to work knowing the terrible could happen - and it did.

'When parliament was under attack they acted with bravery and professionalism.

'They stood on the frontline and did all they could to stop an attacker going any further.

'From those who protected us as we took refuge in our offices to those who looked an assailant in the eye - we are reminded of just what an important role these people we work side by side with play.'