He said: "Both of the (transplant) operations were long and difficult.
"I accept that on both occasions you were tired and stressed and I accept that this may have affected your judgment. This was conduct born of professional arrogance of such magnitude that it strayed into criminal behaviour.
"What you did was an abuse of power and a betrayal of trust that these patients had invested in you.
"I accept that you didn't intend or foresee anything but the most trivial of harm would be caused."
Opening the facts of the case against Bramhall, prosecutor Tony Badenoch QC said one of the two victims initialled by the world-renowned surgeon had been left feeling "violated" and suffering ongoing psychological harm.
Acknowledging that Bramhall's actions had not caused either patients' new liver to fail, Mr Badenoch said: "This case is about his practice on two occasions, without the consent of the patient and for no clinical reason whatever, to burn his initials on to the surface of a newly-transplanted liver."
One of the victims, referred to in court as Patient A, received a donor organ in 2013 in a life-saving operation carried out by Bramhall.
But the donor liver failed around a week later - for reasons unconnected to its implantation - and another surgeon spotted Bramhall's initials on the organ.
A photograph of the 4cm-high branding was taken on a mobile phone and Bramhall, who now works for the NHS in Herefordshire, later admitted using the argon beam coagulator to mark Patient A's liver.
Mr Badenoch said of the initial transplant operation: "Mr Bramhall had to work exceptionally hard and use all of his skill to complete the operation.
"At the end of the operation he performed a liver biopsy using the argon beam coagulator, and then used it to burn his initials."
A nurse who saw the initialling queried what had happened and Bramhall was said to have replied: "I do this."
The court heard that Bramhall later told police he had "flicked his wrist" and made the mark within a few seconds.
"He knew that the action could cause no harm to the patient. He also said that in hindsight this was naive and foolhardy - a misjudged attempt to relieve the tension in theatre," Mr Badenoch said.