Getting manhandled by robbers is quite an unpleasant experience. A man, however, started laughing as his luxury watch was being forcibly taken from him by a gang of thieves one night on a quiet street in Central London.

Metropolitan Police Commissioner Sir Mark Rowley later said the supposed victim was not enjoying the mugging, though.

“As he was being robbed, he was being manhandled and getting quite violent, he said he actually started laughing because he knew what was about to happen to the people robbing him,” Rowley said, according to London-based digital news service LBC.

The man laughing was actually a plainclothes police officer who was the “bait” in the Met operation to catch phones and watch thieves. He was being followed by fellow officers who eventually arrested the robbers.

Police also arrested dozens of thieves wandering the streets in the area, visibly wearing the luxury watches they had stolen from other victims, LBC reports.

The police tactic in Central London’s criminal hotspots — Westminster, South Kensington, Chelsea and Mayfair areas — proved successful. Ben Russell, Met commander for intelligence and covert policing, said that because of the brave cops who volunteered to be the bait and face violent criminals, 27 watch thieves were caught and charged, with 21 of them now behind bars, according to LBC.

One arrest unrelated to watches or robberies was no laughing matter, though.

Thomas Salton, 30, of Brentwood in Essex, was arrested while driving his Range Rover on 1 December last year for possessing gift boxes that he initially claimed contained Christmas presents. Upon inspection by police, however, the boxes were found to contain ketamine or “ecstasy” tablets and 60 canisters of nitrous oxide, ITVX reports.

Salton’s home was subsequently raided, and more ketamine was found, plus 408 canisters of laughing gas. The suspect became the first person to be prosecuted for possession and intent to sell laughing gas, which the British government classified as an illegal drug only last November.

Under the new drug regulation, inhaling laughing gas for a psychoactive or euphoric effect is now an offense, and dealers could face up to 14 years imprisonment, according to the ITVX report.

Salton was sentenced to 35 months in prison at Basildon Crown Court on 19 February after pleading guilty to the charges.