A Beckenham nurse who witnessed a colleague holding a patient in a headlock waited five months to report the assault, a tribunal heard.
Duncan Macleod saw his colleague assault the woman on the Gresham 1 ward – an acute mental health facility at the town’s Royal Bethlem Hospital in Monks Orchard Road.
But he kept silent throughout the police investigation while his colleague, identified only as Nurse X, claimed the patient attacked her, the Nursing and Midwifery Council (NMC) was told.
Nearly half a year later Macleod confessed he heard Nurse X threaten the "vulnerable" patient, and saw her climb on the sofa to get on the patient's back and put her in a headlock.
The NMC’s Janice Burgess said: "A concern was raised in relation to the registrant's conduct in that an incident occurred on the ward on April 22, 2011 where a member of staff, Nurse X, reported that she had been assaulted by a patient.
"The Metropolitan Police were involved."
She noted acting ward manager at the time Sabrina Phillips had talked to Macleod a few days later, but he expressed no concerns about what he witnessed.
However, she added five months later, as a result of the police investigation, Macleod contacted Ms Phillips stating that he could not provide a witness statement supporting Nurse X’s version of events.
The tribunal heard that by not acting immediately the registrant "failed to protect the patient".
Macleod, who did not attend the tribunal in central London, admitted failing to complete a serious incident report in relation to the assault, as well as failing to highlight the inappropriate behaviour.
The nurse also faces two allegations relating to a conviction in November 2011 at Bromley Magistrates' Court for which he received a £500 fine and was disqualified from driving.
Macleod had flipped his car in Towncourt Lane, Petts Wood, and was found with nearly twice the legal limit of alcohol in his blood.
He admitted his convictions prior to the hearing and also admitted a third charge that he failed to hand over the ward medicine keys at the allotted time.
The panel now has to consider whether Macleod is guilty of misconduct, which could see the nurse suspended.
The hearing continues.