ZNA spokeswoman Renée Willems would not specify exactly what type of operation was carried out but confirmed earlier reports that “something was removed that cannot be restored”. The urology surgeon involved was described as a “very experienced and conscientious specialist” at the Jan Palfijn Hospital.

The other man, who was supposed to have the operation, was taken into surgery for an examination carried out under general anaesthetic – the procedure intended for the first man. He was later operated on for his own complaint. Both men were reported to be well.

“This should never have happened,” Willems said. “We regret it to the utmost. The families have been fully informed. We certainly did not keep anything from them.” The ZNA made it clear that the two men are free to bring a complaint of medical malpractice against the hospital and the doctors involved, although so far neither has done so.

Urology is the branch of medicine covering the urinary system and, in men, the reproductive organs. Though the ZNA would not say what the operation precisely involved, it is most likely to have been a full or partial prostate removal, a procedure whose side effects can include incontinence and erectile dysfunction.