A thief stole a tourist's handbag from a London Underground station and then posted her passport back to her home address in the United States.
The bag, holding jewels valued at more than £5,000 ($8,150), was taken from a 73-year-old from California on 7 May.
She and her husband were at King's Cross, waiting for a Piccadilly Line train to Heathrow, when it was stolen.
She obtained an emergency passport so she could return home and five days later she was sent the original.
Her driving licence was also inside an envelope with a postmark from Greenwich, south-east London.
The jewellery was not enclosed.
The valuables had "enormous sentimental value" to the victim and losing them had caused her "a great deal of distress", British Transport Police said.
A video still of a suspect officers want to speak to about the theft has been released by police.
It shows a slim man thought to be in his early 20s.
He was wearing a grey Adidas tracksuit with a baseball cap, a yellow high-visibility vest and he had a black Adidas rucksack.