Security fears have been raised after it emerged that the gate of Parliament were left unmanned and open in the immediate wake of Wednesday's terror attack.
As armed officers swarm the forecourt, having shot dead terrorist Khalid Masood, the imposing 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 the attack might have been worse had Masood been followed by accomplices.
Pedestrians are shown walking past and at one stage a courier on a moped appears to enter unchallenged.
Yards away, separate footage showed Theresa May being rushed from the building and into a waiting car.
Although the gate was open for a matter of minutes, critics will use the brief security lapse to rebuke claims on Friday by Scotland Yard's anti-terror chief that current arrangements were "proportionate".
Mark Rowley said that procedures for guarding Parliament had been designed so they were not "overly intrusive".
"Our current arrangements have been developed with Parliament over many years and are designed to provide access to the seat of our government balanced with security that is proportionate but not overly intrusive," he said.
Parliament's main entrance has two sets of large metal gates allowing vehicles to go in and out of the estate and they have traditionally been left open during the day.
A pair of smaller, makeshift gates was introduced more recently with two police officers at each to check passes and allow cyclists, cars and delivery drivers to come and go.
Just inside the entrance gate, armed police are usually present and an unarmed officer sits in a booth by the exit.
Electronic ramps are depressed and barriers lifted further into the courtyard after passes are checked using handheld machines which flash up with a picture of the passholder.
More police, some armed, are usually present after the final checkpoint.
Wednesday’s murderous rampage at Westminster left five people dead, including the attacker. Many more were injured.