Detectives in Southwark are appealing for the public's help to identify one of two men who conned an elderly woman out of her savings.
The victim, who is 71 and lives in Camberwell, was first contacted by a man on Wednesday, 6 December.
She received a phone call and the caller told her that he was a police officer and he needed her to help with a sting operation.
He deceived her into going to a bureau de change in the West End to buy some Euros and arranged a place to hand them over.
She gave nearly five thousand pounds in Euros to a male suspect in Buckingham Palace Road, SW1 at around 17:00hrs.
She was then contacted again the same day and went to Oxendon Street, SW1, where at 20:29hrs she handed over thousands more in Euros.
The following day the victim was contacted again and was told her help was needed once more.
This time, between 11:20hrs and 12:00hrs, on Cadogan Gardens, Sloane Square, SW3, she handed over £7000 in Euros to a second suspect.
In total, the victim is out of pocket by over £24,000.
The first suspect is described as an Asian man about 5ft 8ins and in his 20s.
Police are releasing CCTV and an image of the first suspect involved in the fraud.
DC Michael Esangbedo of Southwark CID, said: "This was a cruel and heartless deception practised on a vulnerable, elderly woman. These men have clearly targeted the victim and I have no doubt that unless they are arrested they will continue to prey on the elderly and vulnerable. These men need to be caught and I would ask anyone with information to contact police or Crimestoppers immediately."
Any witnesses or anyone with any information is asked to call police on 101 or contact via Twitter @MetCC - please quote 3036717/17
To give information anonymously contact Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.