Security must be stepped up at the Palace of Westminster after Wednesday’s horrific terror attack, parliamentarians have said.
The calls to enhance safety measures came as footage revealed the palace’s gates were left open and unattended in the immediate wake of the atrocity.
The footage, captured by The Times, shows the aftermath of the assault on New Palace Yard which left Pc Keith Palmer mortally wounded. Three other innocent people were also killed.
As armed officers swarm the cobbled forecourt having shot dead terrorist Khalid Masood, the iron gate that allows vehicles to enter can be seen wide open.
No police officers are visible guarding the entry point, known as Carriage Gates, fuelling concern that the attack might have been worse had Masood been followed by accomplices.
The video shows pedestrians walking past and at one stage a courier on a moped appears to enter unchallenged.
Yards away, separate footage showed Prime Minister Theresa May being rushed from the building and into a waiting car.
Former Metropolitan Police commissioner Lord Blair and ex-House of Commons deputy speaker Nigel Evans both said security will now have to be stepped up.
Lord Blair told BBC Radio 4's Today programme: "I am absolutely certain that there will be a review now of the outer soft ring that those of us who work at the Palace of Westminster are very used to.
"Always behind it is the inner core of armed officers, but Pc Keith Palmer has paid with his life for that soft outer rim and I think that his family at least, and everybody else, needs the reassurance that will be reviewed."
Lord Blair refused to criticise the officers who apparently left the gate unguarded, describing them as "human beings" who will have been "gripped completely" by the attack while knowing the "cavalry" of armed officers was on its way.
But he added: "I'm absolutely certain that there will have to be changes.
"People are used to the fact that if they go into Downing Street they are confronted by basically closed gates and armed officers and I'm afraid that's what will have to happen, but we'll leave it to the reviews to see what it is.
"But I don't think there should be shock horror about the fact the gates were open for a moment after that kind of attack."
Mr Evans described the outrage as "one of those things that by experience you learn" from.
He revealed that "lots" of MPs locked in the Commons chamber during and after the attack were discussing how to boost security in certain areas.
But he said far more checks are carried out at Carriage Gates than we he was elected in 1992, when a police officer would just "wave you through".
The Tory MP told Today: "I've got no doubts whatsoever that there will be enhanced features of security, it's happening on a regular basis.
“But following this tragedy, security has got to be upped at the same time as still having a welcoming hand to members of the public to come and see how democracy works."
The video comes after Scotland Yard's anti-terror chief Mark Rowley said current arrangements were "proportionate".
On Friday, he said that procedures for guarding Parliament had been designed so they were not "overly intrusive".
Parliamentary authorities and the police are carrying out a review of security in the wake of Wednesday’s bloody assault.
The horrifying attacks left five people dead, as Masood ploughed through pedestrians on Westminster Bridge before crashing through Parliament gates.
It was there that he stabbed to death unarmed police officer Keith Palmer before he was stopped, shot and killed.