The St Albans MP said she was “sickened and appalled” by the terrorist attack outside Parliament.

Five people died after Khalid Massood mounted the pavement on Westminster Bridge yesterday, hitting a number of pedestrians before getting out of the car and stabbing a police officer.

Anne Main said PC Keith Palmer, who died yesterday afternoon, was a “brave man, doing his job”.

The MP was in Parliament when the attack took place and was locked in for five hours while security services made sure the building was safe.

She said: “As the dramatic events were unfolding outside the House of Commons chamber, we were held and protected by the brave and diligent Houses of Parliament security staff. I am truly grateful for their work, keeping all members of staff safe.

“The police officer who was tragically killed was a brave man, doing his job by protecting our parliament and the people inside. I pay tribute to him and all the security services on the estate who put themselves on the line, and my thoughts are with his family.

"The death of innocent victims has sickened us all. My heart goes out to all their loved ones and those who were injured.

"This was an attack not just on our parliament, but also on our country and our values.

“Free speech, liberty, human rights and the rule of law were under assault. I believe that our country will never waver in the face of terror, and that these values that we all hold so dear will always prevail.”

Eight people have been arrested in connection with the incident, which is believed to be be linked to Islamic terrorism.