On 22 March 2017, while acting as Commissioner of the Metropolitan Police, Mackey was on a routine visit to the Palace of Westminster. He was there during the 2017 Westminster attack and was described as a "significant witness". As a result of this, it was claimed he could not issue any public statements, including any responses to negative commentary regarding his conduct. Much of that negative commentary compared Mackey’s actions unfavourably with those of the armed protection officer who shot Khalid Masood (the attacker) dead. Gaby Hinsliff in The Guardian wrote: “A Met chief stayed in his car during an attack. That’s not leadership.” Her article stated that “………. what apparently most enrages those officers now condemning Mackey is a sense that their own leaders wouldn’t do what is asked of them every day, and that perhaps speaks to a more deep-rooted sense of betrayal going back years. It’s horribly unfair to call Craig Mackey a coward, particularly from the safety of civilian armchairs. He made what was in all probability the cowardly decision. But it does not, somehow, look like the decision of a leader. In fact it stinks of the 'do as I say, not as I do' double standards of today's politically sensitive police service management.”