A surgeon has been suspended for six months after the General Medical Council found he was guilty of misconduct.
Gideon Lauffer, of Hendon, was sanctioned after a series of botched operations.
The GMC heard that two patients had died and a third lost a testicle after Mr Lauffer "acted outside his area of competency".
Concerns were first raised about his performance in 2004, but the GMC then decided he should be allowed to continue working while improving his abilities.
Last year Barking, Havering and Redbridge University Hospitals NHS Trust sacked Mr Lauffer after colleagues lost confidence and trust in him.
He was suspended from practising while the investigation took place.
A GMC panel heard that Mr Lauffer, who was a former Hampstead Garden Suburb Synagogue youth service leader, was a "respected and competent surgeon" who had given "many years of dedicated service".
But it found he had been dishonest in performing a procedure when he was already prohibited from doing so and that he had conducted another operation "without having undergone any formal training".
The GMC concluded: "The panel is conscious that it is important to demonstrate to you, to the profession and to the public that your misconduct cannot go unmarked."
Mr Lauffer denied accusations of incompetence, delaying surgery and performing incorrect procedures. He admitted carrying out laparoscopic surgery procedures despite being banned.
His fitness to practise will be reviewed at the end of the suspension period.