The founder of a private drug treatment clinic has been struck off the medical register.
The GMC hearings began in 2004
Dr Colin Brewer, who headed London's Stapleford Clinic, was found guilty of serious professional misconduct by the General Medical Council (GMC).
He had faced allegations of inappropriate drug prescribing for patients with addictions.
The case began in 2004, and was brought after a patient died after being sent home with a "DIY detox" kit.
Grant Smith, 29, from Northampton choked on his own vomit in his sleep in September 2001 after taking the cocktail of drugs, including diazepam, rohypnol and temazepam.
In its judgement, the GMC panel said Dr Brewer, who is now retired, fell "seriously short of the standards expected of a medical practitioner".
It added: "On numerous occasions your practice was found to be irresponsible."
The Stapleford Centre treats people addicted to heroin, alcohol and other drugs.
Dr Brewer said he "deeply regretted" Mr Smith's death.
But he added: "I am pleased that the GMC has recognised that I have made some important contributions to addiction medicine, and that the Stapleford Centre is continuing its work under the direction of Dr Ron Tovey."
He said he had accepted during the GMC that he had made mistakes, but said the clinic had been trying to provide a service which was not available on the NHS.
Dr Tovey and another doctor who worked at the clinic, Hugh Kindness were also found guilty of serious professional misconduct by the GMC.
Dr Kindness, who is also retired, received a reprimand from the council which said he inexperienced in the management of drug misusers and had been guided by his colleagues.
Dr Tovey has had conditions attached to his licence to practice for the next three years.
The GMC said it recognised he had taken steps to modify the way the clinic operated.
In a statement, he said: "I have dedicated my professional career to the treatment of patients suffering from drug addition and I have always tried to act in the best interests of my patients.
"I am delighted that the GMC has decided that I should remain on the medical register and continue to provide treatment to my patients.
"I will now take time to reflect on the determination and will consider the conditions set out by the GMC."
Four other doctors who worked at the centre had previously been cleared of serious professional misconduct.
The case involved the largest ever number of doctors to be jointly charged in a GMC case.