Two young men masquerading as policemen were caught red-handed when they picked on the wrong target - a plain-clothes police constable - in a bungled hold-up in Tai Po early yesterday. The two muggers, aged 19 and 20, did not believe their victim was a police officer - even though he produced his warrant card - and tried to snatch his wallet before they were subdued. The constable was one of five plain-clothes officers carrying out surveillance of a park near the Kwong Fuk Estate in Tai Po, where a teenage couple were robbed by three youths on Tuesday night. The two men were seen arriving in the park soon after midnight. Officers kept an eye on them, as they were behaving suspiciously and their descriptions matched the robbers of the teenage couple. 'They were apparently looking for targets, as they kept circling around the park,' one officer said. 'We believe they preyed on younger people.' After searching for about 45 minutes and failing to find a target, the two men left the park and were followed by the constable. On reaching Plover Cove Road, they turned and stopped the officer. 'They showed what they claimed were police passes and demanded that the constable hand over his wallet,' the officer said. 'The constable then identified himself as a police officer and presented his warrant card, but the pair did not believe him and then tried to snatch his wallet.' The two men scuffled with the constable before his four colleagues rushed up and subdued the pair. The constable suffered minor injuries to his hands and face in the incident and was treated in hospital.