Cash was taken from the 65-year-old victim’s account after the incident in Corporation Street between 11am and 11.30am on Monday, April 25.
Now, nearly a month on, police are appealing for help to catch the offender.
The victim had used a cashpoint when he was distracted by a man who said he had dropped a £10 note on the floor.
The victim bent down to pick up the note, at which point his cash card, which was still in the cashpoint, was swapped with another.
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A short time later cash was removed from the victim’s bank account.
The offender was white, about 5ft 8in, of medium build and with short brown wavy hair.
He had sideburns and was wearing a light grey padded waist length jacket, blue jeans and yellow boots.
Witnesses or anyone with information about this incident should contact police on 101 or Crimestoppers anonymously on 0800 555111.