A coroner has criticised the Royal Free Hospital after a medic injected a pensioner with an overdose of insulin during an operation.

Patrick Moran, 70, was admitted to the hospital in Pond Street, Hampstead, on July 27 last year suffering from pain in one of his legs, gangrene on his toes and a narrowing of his blood vessels.

Mr Moran, a bachelor who lived in Mornington Crescent, was taken into an operating theatre where doctors widened arteries his lower back.

During the operation, he had to be administered with an insulin-dextrose infusion after potassium levels in his blood rose to above normal levels.

But an anaesthetist used the wrong syringe and injected Mr Moran with 100 units of insulin instead of 10.

St Pancras assistant coroner Jacqueline Devonish has issued a prevention of future deaths report following Mr Moran’s inquest.

The report reveals that instead of an insulin syringe the medic used a normal one millilitre variety.

It adds that the use of that type of syringe was “common practice” within the hospital’s anaesthetic department even though the NHS had issued a warning about the possibililty of misuse in June 2010.

In a second criticism, the report notes the Royal Free Hospital removed diabetes training for staff as a compulsory requirement.

It says: “As a result there is currently no mandatory training provided to doctors within the Trust to advise them of use of insulin specific devices when drawing up and administering insulin,” the report states.

The hospital is also slammed for not having a process in place to ensure it is up to date with NHS public health messages and patient safety alerts.

“There is a risk that future deaths will occur unless action is taken,” Ms Devonish states.

Mr Moran, who was in the building trade, initially made a good recovery after the op but his lower left leg later had to be amputated. His lower right leg then deteriorated, but it was decided “further interventions would be futile.” The coroner’s verdict attributed the death to natural causes.

Expressing condolences to Mr Moran’s family. a spokeswoman for the Royal Free said: “We always look to learn from any death in our hospitals and have responded with an action plan to address the concerns raised.”