The Watford Observer received a video of a loud alarm going off inside the centre, which the venue has now confirmed was not due to an actual emergency.
A spokesperson for the Harlequin said: “Today, the centre was evacuated as part of a routine training exercise.
“The safety of our visitors, our staff and our retailers’ employees is a number one priority and we review and test our procedures and policies continually to make sure high standards are always met.”
A similar drill took place in June of last year, with customers briefly evacuated as part of the exercise.
The centre returned to its original name last summer, having previously had spells as Intu Watford and atria Watford.
It recently hailed a “record breaking footfall” of 17.2 million for 2025, bucking the national trend.
British Retail Consortium data shows UK shopping centre visitor numbers declined 5.1 per cent year-on-year in December 2025, but The Harlequin’s grew 1.5 per cent.