Great train robber Ronnie Biggs has complained that up to £100 cash has gone missing from his nursing home room.
The gravely ill 81-year-old told staff at the home in Bells Hill, Barnet, north London, that the money disappeared from a stash near his bed.
They contacted local police, who were planning to investigate further before the alleged crime is recorded.
One source told The Sun that the suspected theft is the talk of the care home and Biggs has "finally got his commeuppance".
But son Michael Biggs said he was not aware of the claims and said he did not know his father kept money in his room.
Asked about the robber's health, he said: "He is OK, he is hanging in there. He is very ill and as well as could be expected."
Mr Biggs added that his father could die "at any moment" and can communicate only through a word board.
The former outlaw was released from prison on medical grounds last year and has been living at the Bells Hill care home since.
Originally from Lambeth, south London, he was a member of a gang that made off with 2.6 million from a Glasgow to London mail train in 1963.
Biggs was given a 30-year sentence but escaped from Wandsworth prison, south London, in a furniture van after spending 15 months in jail.
He was on the run for more than 30 years, living in Spain, Australia and Brazil before returning to the UK voluntarily in 2001.
A Metropolitan Police spokesman said no formal allegation has been made but inquiries continue.
He said: "Officers were notified on Tuesday of an alleged theft from an 81-year-old resident of a care home in Barnet."
The manager of Carlton Court Nursing Home was not available to comment.