Face-to-face fundraisers are being warned about a man who - unlike many members of the public - signs up for multiple direct debits to charities for as much as £1,000 a month.
The fly in the ointment is that the payments fall through because the bank details, phone numbers and addresses are false or unverifiable.
The Public Fundraising Regulatory Association has warned its members about the man, who uses the name "Liam Traynor". The PFRA said it was alerted by a fundraising agency and had discovered that he had completed at least 11 direct debit mandates across London in recent weeks.
It also established that a 19-year-old man with the same name and similar appearance received a suspended prison sentence last month for fraudulently obtaining nearly £20,000 worth of first-class rail travel.
The man making direct debits has not replied to emails from Third Sector and the phone number given to one of the fundraisers does not work.
Trading standards sources say he is unlikely to be committing a crime because no one is being defrauded, but action might be possible on the grounds that he was harrassing street fundraisers.