Lawyers from Birmingham firm Anthony Collins have won a victory for the family of David Gray, the man killed by an overseas doctor.

A coroner ruled today that Mr Gray was unlawfully killed after he was given a fatal overdose by an overseas locum.

His death amounted to gross negligence and manslaughter, said Cambridgeshire North and East Coroner William Morris.

In a damning conclusion to the 10-day inquest, the coroner described German doctor Daniel Ubani, who treated Mr Gray, as "incompetent and not of an acceptable standard".

Mr Gray, 70, died after he was injected with 100mg of diamorphine – 10 times the recommended daily dose.

The inquest heard that Dr Ubani was working on his first out-of-hours shift in Britain and had only arrived in the country the day before.

He will not face charges in the UK because the German government refused an extradition request, instead giving him a nine-month suspended sentence and ordering him to pay a fine of 5,000 euros.

Mr Gray’s family was represented at the inquest by Inez Brown, from Anthony Collins.

She said: "David Gray was killed unlawfully when Dr Ubani gave him a lethal overdose of diamorphine but communication breakdowns between the UK and German authorities mean that he is now immune from prosecution in this country.

"Patently someone should be held to account for Mr Gray’s death and we will be advising the family on possible next steps.

"Regrettably it has taken David Gray’s death to highlight that current regulations for the employment of EU doctors in the UK and the procedures adopted by primary care trusts and some out-of-hours agents are simply not robust enough, compromising patient safety. Despite differences in training and a lack of familiarity with the NHS, doctors from Europe, are subject to less stringent checks than doctors from anywhere else in the world."

Mr Gray’s son, Dr Stuart Gray, himself a GP, added: "Every doctor used for out-of-hours care should be properly trained for the job and every one should be able to speak English, common sense requirements, which Dr Ubani failed to meet.

"My father’s tragic death happened because of his actions and because of serious failings within the Cambridgeshire Primary Care Trust and Take Care Now. We want to see someone tried under UK law for his death but we also want to see safeguards put in place nationwide to prevent this happening again."