The 3D projection, on display nightly between 7pm and 10pm in Jeo-dong Park, appears every two minutes to warn: “In case of an emergency, the police will be dispatched in real time. CCTV is installed here.”

“If you look closely, you can see that it is not an actual police officer,” admitted Ahn Dong-hyun, the chief of Jungbu police station. “But it has been confirmed that the mere presence of a hologram can reduce the possibility of crime.”

Officer Kim Hyun-don of Jungbu police said: “The biggest impact was on impulsive crimes such as drunken violence or disputes.”

Ed Flahavan of the UK’s Behavioural Insights Team described it as a “particularly novel way to increase police presence, even if none are actually there”. He added: “In behavioural science, using police as a deterrent to reduce crime is about increasing the perceived likelihood of criminals being caught.”

Cambridge criminologist Lawrence Sherman said: “Holograms are probably much more compliant as well since the police don’t always want to go to the places they are assigned to control. But a hologram can’t catch you. It can’t put handcuffs on you and take you away. And criminals know that. Certainly, the question of what the initial effect might be of that versus the long-term effect is unclear and it will surely lose its power of deterrence after a while.”