A north London NHS trust performed surgery on the wrong patient last year - and gave another the “wrong implant/prosthesis”.
The incidents were among six ‘never events’ recorded by the Royal Free London NHS Foundation Trust between April 1 and November 30, 2022.
The trust - which runs the Royal Free in Hampstead, as well as Barnet and Chase Farm hospitals - has not released further details of the procedures but said “no serious harm arose”.
Never events are defined as “serious, largely preventable patient safety incidents that should not occur if healthcare providers have implemented existing national guidance or safety recommendations”.
Further incidents were two cases where an incorrect skin lesion was excised, a misplaced nasogastric tube and an injection administered in the wrong place.
The incidents were revealed following freedom of information requests to NHS hospital trusts across the country by medical negligence firm Blackwater Law.
A Royal Free London spokesperson said: “The Royal Free London NHS Foundation Trust has an open and transparent culture regarding patient safety incident reporting, and - like all NHS trusts - routinely reports never events when they occur.
“We have apologised to those affected and whilst no serious harm arose, events like these are always thoroughly investigated to reduce the risk of them being repeated in the future. Never event data from all trusts is published by NHS England on their website.”
Other London trusts recording never events during the period included at Lewisham and Greenwich NHS Trust, which had four. Barking, Havering and Redbridge University Hospitals NHS Trust; Guy's and St Thomas' NHS Foundation Trust; Homerton Healthcare NHS Foundation Trust; King's College Hospital NHS Foundation Trust; and North Middlesex Hospital NHS Trust each recorded three never events.
Jason Brady, partner and head of Blackwater Law, said: “It is concerning to see the details of these never events.
“At Blackwater Law we see the impact that these incidents have, not just on the person affected, but also on their families.”
The Care Quality Commission currently rates the Royal Free and Barnet General hospitals as ‘requires improvement’, while CHase Farm is rated ‘good’.