John Stalker, the former deputy chief constable of Greater Manchester Police, has died, the force and his family have announced.
Mr Stalker, who was 79 and living in Lymm, Cheshire, was widely known for his investigation into an alleged 'shoot to kill policy' in Northern Ireland during the Troubles - known as the Stalker Inquiry.
He was appointed to head the 1983 independent investigation into the conduct of the Royal Ulster Constabulary after allegations IRA suspects were shot dead by RUC officers during the 1980s.
Mr Stalker was removed from the inquiry however shortly before it was due to report in 1986 - prompting an infamous controversy known as the 'Stalker Affair' that continued for years and sparked public outcry
He was taken off the case at the moment he believed he was about to obtain an MI5 tape of one of the shootings and went on to be accused of associating with Manchester criminals, allegations he was later completely exonerated of.
His report was never published but papers released in 2016 revealed he confided to a diplomat that he had uncovered evidence of 'six murders' during his investigation.
At the time there were conspiracy theories that he had been close to uncovering murky truths that went right to the heart of government.
Mr Stalker retired in 1978 after more than 30 years of service with GMP.
As a detective constable he worked on the Moors Murders inquiry involving Myra Hindley and Ian Brady and on the investigation into the 1985 Manchester Airport disaster, in which 55 lives were lost when a passenger jet bound for Corfu caught fire on the runway before take-off.
His family confirmed his death on Friday in a statement issued by GMP.
Colette Cartwright, his eldest daughter, said: "Our dad John was a beloved husband, grandfather and great-grandfather who enriched the lives of many.
"After marrying my dear mum Stella in 1961 he spent his life as a devoted police officer, proudly serving the people of Greater Manchester for over 30 years.
"He is fondly remembered by many as going above and beyond the call of duty and was committed to making a difference for those most in need. As testament to this, he devoted his life to a career in CID where he worked for 16 years, rising to the rank of Detective Superintendent.
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"Respected by many of his colleagues, he had a varied career and held posts in the Serious Crime Squad and the Bomb Squad.
"He also became the first head of the drugs squad.
"In 1978 - aged 38 - he was appointed head of Warwickshire CID, the youngest Detective Chief Superintendent in the country - later becoming Deputy Chief Constable of the Greater Manchester Police in 1984, the biggest police force in the provinces.
"This is something that my dad worked so hard for and we, as a family, will always be immensely proud of his accomplishments."
The family said he travelled the world studying terrorism and crime and carved a new career in journalism when he retired from police service.
He wrote columns for national newspapers, published an autobiography in 1988 and later worked in the media and television.
Mr Stalker was also involved in investigating the high-profile murders of Jill Dando and Millie Dowler after retirement.
Mrs Cartwright added: "My mum and dad were great partners and enjoyed nothing more than travelling the world.
"They enjoyed spending time at their holiday home in North Wales, spent many holidays in South Africa and held precious memories of spending time together exploring new places.
"I’d like to thank all those at Greater Manchester Police who are helping us through this incredibly difficult time and I think their support is reflective of the spirit of my dad and his commitment to policing throughout his life.
"My dad will be sorely missed by all lives he has touched both professionally and personally. We will always be proud of him and everything he achieved. We love him and will miss him so much."
