A man was mistakenly circumcised at one of Leicester's hospitals.
The patient was meant to be having a cystoscopy - a procedure to look inside his bladder using a thin camera.
The error was revealed in a report produced by the Clinical Commissioning Group compiling so-called 'never' events - named because they're largely preventable and should never happen.
There were at eight incidents at Leicester's hospitals last year.
Others included a swab being left in a child after a surgical procedure and the wrong patient having an operation after a notes mix up.
The Trust said they're deeply sorry to those patients involved say they're committed to making improvements.
The eight never events to happen at hospitals ran by University Hospitals of Leicester NHS Trust in 2018:
A swab was left in a child who had had an adenoidectomy - a surgical procedure to remove tissue from behind the nasal passages.
Wrong patient surgery - two patients with similar name notes merged into one meaning the wrong person had an operation.
A patient consented to the wrong surgery due to the consent process not being adequately robust.
Two cases of unintentional connection of patient to requiring oxygen to an air flowmeter.
A patient had a wrong site angiogram. Failure to learn from a previous never event was listed as a contributory factor.
A man was circumcised when he had actually consented to cytoscopy. Failure to learn from a previous never event was listed as a contributory factor.
Wrong implant/prothesis - the wrong side hip nail was implanted in a patient.
When asked how the circumcision incident was allowed to happen, UHL did not provide an answer.
The document detailing the incident, which occurred in September 2018, said one of the key contributing factors was failure to learn from a previous never event.
The trust released this statement:
We remain deeply and genuinely sorry to those patients involved, and of course we have personally apologised to each one.