The methodology of the Westminster attack is consistent with the current trend across mainland Europe of extremists using a vehicle and weapons against crowded places at iconic sites, targeting figures of authority such as the police. As the UK threat level was not raised after the attack it is a likely sign Khalid Masood acted alone and the incident was not part of a coordinated campaign. This may be corroborated as the 12 people arrested after the attack have now all been released without charge.
Prior to the incident, Islamist extremists appeared to have shown little interest in mounting attacks against the Government Security Zone or Government Estate. Whilst iconic government sites and individuals have featured in Islamist extremist media, overseas encouragement for their targeting appeared aspirational and not linked to credible attack planning in the UK. Masood, however, specifically targeted Westminster above other locations after driving from Brighton that day.
It is highly likely Masood sought maximum casualties by using the vehicle in the manner he did. His approach over Westminster Bridge afforded an acceleration route not possible from the opposing Parliament Square direction. By driving the full length of the bridge (around 250 metres) in a zig-zag formation and reaching a reported speed of 76mph, Masood was able to intentionally use the kinetic energy of the car to cause mass casualties. Armed-police vehicle check points, previously held on both Westminster and Lambeth bridges, were absent which is noticeable considering other road based mitigation measures recently implemented in the capital. Those include road closures and barrier installations around Buckingham Palace for the Changing of the Guard ceremony.
Hostile vehicle mitigation measures have been a long standing part of security architecture in the UK, either overtly with bollards and fences or covertly with concealed protection afforded through innovative and decorative building designs. The attack highlights the extent to which those designs may now need to be extended around buildings or sites to include the approach roads and pavements, thereby affording protection to members of the public and potentially employees attending the site, rather than the actual building which has been the traditional target for attacks.
The timing, audible impact of the vehicle against the perimeter fence and the likely surge of pedestrians towards Parliament Square are relevant factors in the attack. The timing may lead to a review of the police patrol strategies. The noise and location of the impact could have been an initial distraction to the police, potentially directing their attention away from Carriage Gates. The likely surge of pedestrians away from the vehicle would have been in the direction Masood ultimately ran, thus potentially concealing him within a crowd. An indication of the amount of people present in the area may be derived from the 1,500 potential witnesses cited at the opening of the inquest into Masood’s death at Westminster Coroners Court.
The staffing of Carriage Gates by unarmed police was routine, with their primary role likely to be affording the entrance or exit of vehicles from the Palace grounds and managing the pedestrians at the roadside. Close-armed support would be provided by both static and patrolling armed officers nearby. Numerous media reports suggest the gates were subject to an existing security review, awaiting local authority planning permission for physical changes.
Whilst it is not currently clear if police officers were Masood’s intended target, it is likely considering the probable Islamist extremist rhetoric to the incident, supported by the attack in Paris on 20 April 2017. Notably, whilst Daesh claimed Masood as “a soldier of the Islamic State”, he was not specifically named unlike the Paris attacker, Karim Cheurfi. This may suggest that whilst Masood was inspired by Islamist extremism, he was not under overseas direction and control.
The use of knives in the attack is typical of current methodology in the UK. Such weapons do not require any formal training and the implements are easy to obtain. They have frequently featured in counter-terrorism cases, with a disrupted plot in Birmingham on 29 March 2017 involving a further intended knife attack by an Islamist extremist. Use of firearms or explosives by extremists in the UK remains less likely, due to gun control laws and penetration of criminal networks by law enforcement agencies.