Christopher Reid, the managing director of Security Search Management & Solutions (SSMS), said he was “absolutely gutted” and that the mistake, which has cost Manchester United £3m, was entirely his.

“I am absolutely devastated that a lapse in my working protocols has resulted in many people being disappointed, frightened and inconvenienced. Nothing I can say will rectify that,” said Reid, who worked for the Metropolitan police service’s specialist search unit for 26 years, before retiring in 2011.