MPs have said the Carriage Gate, scene of Wednesday’s deadly attack, was the weak spot in parliamentary security as Defence Secretary Michael Fallon insists a review will take place.
The attack, which led to four deaths, including the attacker, and 40 injuries, took place first near, and then at and through, the Carriage Gate into New Palace Yard.
The gate is usually guarded by only four officers and left ajar because it is in constant use.
“It’s a terrible, terrible day for Parliament, the one weak spot on our estate is those carriage gates,” Labour MP Mary Creagh said.
“We have four police officers there, two on the gate going in, two on the gate going out, we see them every day, we are friends with lots of them.”
One officer on the gate, Keith Palmer, died from stab wounds at the scene following the attack.
“I think we will need to look at security at the Palace [of Westminster] in the wake of this incident, but that is a plan for another day,” Creagh said.
“I think tonight we need to be remembering all those who have been caught up in today’s tragic events.”
Conservative Iain Duncan Smith told the Telegraph he it was a “little bit of a surprise” the officers on the gate were unarmed.
Former civil service Chief Lord Kerslake called for “a complete overhaul of security from top to bottom.”
On Thursday, Fallon told the BBC that a review would be carried out but that “Parliament cannot be hermetically sealed, people are coming and going all the time.”
“Obviously this is something that will be reviewed by the house authorities,” he said, adding that these kind of low-tech, lone wolf attacks were “difficult to forestall.”
“And we are dealing with a terrorist enemy that is not making demands or holding people hostage, but just to kill as many people as possible.”
Royal United Services Institute (RUSI) experts added that Wednesday’s attack was part of the “new norm” and that more incidents of extremists using similar tactics were inevitable.
“Attacks of this nature, the willingness of someone to use everyday objects, cars, knives, are incredibly difficult to prevent,” RUSI research fellow Emily Winterbotham told AFP news agency.
“We can do everything as far as possible to prevent them but they do happen and we need to prepare for that in order to respond in an appropriate manner.”
The probability of terrorists using household objects to carry out attacks is also ever higher as guns and explosives have become too hard to obtain in European countries.
“Strict gun-control laws in the UK, and the difficulty of acquiring automatic weapons, even on the black market, decreases the likelihood of mass-casualty shooting attacks,” said Jane’s Terrorism and Insurgency Centre spokesman Otso Iho.
“The risk that vehicular attacks will therefore be used as the most likely tactic of a lone actor intent on conducting mass casualty attacks in the UK is elevated.”
Home Secretary Amber Rudd responded to criticisms that the New Palace Yard gate was a weak security spot on Thursday afternoon, telling the BBC that seeing the attack as an intelligence failure was “absolutely the wrong judgement.”