A gang of thieves targeted an 86-year-old widow shopping in a supermarket and then squandered her life savings on cars and fast food, police said.
One of the men was caught on CCTV leaning over to watch as the victim entered her PIN while buying groceries at Waitrose in Wandsworth, south-west London.
He is then seen recording the code in his phone as the unsuspecting pensioner leaves the store.
An accomplice lying in wait outside the shop allegedly distracted the elderly woman by posing with a map pretending to be lost, allowing another to take her card from her pocket.
The thieves then went on a spree totalling £21,000, buying clothes, six second-hand cars and fast food meals, according to police.
"The money was the victim's life savings that she was keeping for her grandchildren," a Metropolitan Police spokesman said.
"The theft has also had a significant impact on the victim, leading her to change her usual routine. She is also afraid to get her bank card out anywhere in public."
He added: "As the 86-year-old widow was shopping in the store, two men and a woman watched her as she paid for her shopping.
"One of the suspects saw her enter her PIN code and recorded the numbers on his mobile phone.
"Once outside the store, another of the suspects distracted the victim stating he spoke little English and pretended to be lost with a map, as another stole her bank card from within her pocket.
"The victim's bank card was used to purchase £21,000 worth of cars, clothing and a restaurant meal."
Officers are appealing for any witnesses or anyone who recognises any of the suspects on the footage to come forward.
They are described as: a white woman in her 40s, wearing glasses, a black and white head scarf, dark coat, white blouse, dark leggings, black boots and carrying a large brown bag; a slim-built Asian man in his 20s, wearing a dark hooded top with a fur hood liner, dark jeans and white trainers; and another Asian man, in his late 30s and of medium build, wearing a dark hooded top with a light blue liner and white zipped front, dark jeans and white trainers.
The theft is believed to have taken place between 10.30am and 12.20pm on Thursday March 17 in Balham High Road in Wandsworth.
Anyone with information can call officers in Wandsworth on 101, quoting reference 0306003/16 or Crimestoppers anonymously on 0800 555 111.