Leslie went to Queen's University in Belfast and did his early surgical training in N Ireland.

Training in cardiothoracic surgery continued in Leeds and, wanting to specialise in paediatric cardiac surgery, he spent a year at Gt Ormond St Hospital in London before being appointed as a Consultant at the Freeman Hospital in Newcastle upon Tyne.

Giving evidence to the Bristol Inquiry stimulated an interest in the interaction of the law with clinical practice and this prompted an LLM in Medical Law via distance learning. Frustrated with things which he thought could be better, he got involved in the "politics" of medicine. This led to unexpected leadership opportunities - as Chair of the Intercollegiate Exam Board, President of SCTS (Society for C-T Surgery), Council member of the Royal College of Surgeons and later, Chair of the Independent Review of Gross Negligence Manslaughter commissioned by the GMC. The background in Medical Law led to teaching opportunities which opened the door to appointment as Assistant Coroner (which he still does).