Sir John Hermon, the former Chief Constable of the Royal Ulster Constabulary, has died aged 79, his family announced today.

The husband of North Down Ulster Unionist MP Lady Sylvia Hermon had fought a long battle with Alzheimer’s disease.

A statement said: “It is with enormous sadness that the family of Sir Jack Hermon announce his death, after a long and valiant struggle against the ravages of Alzheimer's. He passed away very peacefully at teatime yesterday (Thursday) in a nursing home in Bangor.

“Members of his immediate family, including his wife, Sylvia, had been with him throughout the day.”

In a policing career stretching over four decades — he joined the RUC in 1951 — Sir John headed the police force for almost the entire 1980s, during one of the most turbulent periods of the Troubles, which included the shoot-to-kill inquiries and sustained republican and loyalist terrorist campaigns.

Among many tributes today First Minister Peter Robinson said: “He was to the fore of the battle against terrorism and he played a leading role in stamping it out. As well as being a tough, professional police officer, Sir Jack was also a committed family man.”

And former colleague, Assistant Chief Constable Alan McQuillan, said: “He set the very highest standards for himself and expected nothing else from anyone else. This did not always make him popular but I think when history looks at the RUC it will look favourably at Sir Jack Hermon.”

There were no immediate details of funeral arrangements.

“Sir Jack Hermon was a huge figure in the history of the RUC,” added Mr McQuillan, who served with him and later led the groundbreaking Assets Recovery Agency.

“(He) was a very energetic and dynamic leader, but when you got to know him you saw he was driven by a total passion for impartial policing, for protecting the community and an immense pride in the men and women who served in the RUC.”

Mr McQuillan said the former chief had led the reforms that flowed from the Hunt Report, and throughout his career played a key role in developing the RUC.

Tributes from the political world were led by the former First Minister Lord Trimble.

“Sir John Hermon will always be remembered as an outstanding Chief Constable and a man who did great service to Northern Ireland during the Troubles,” he said.

Secretary of State Shaun Woodward, extending his sympathy and condolences to Lady Sylvia, said: “Through a long and distinguished career, Jack Hermon earned deep and lasting respect.

“He was undoubtedly a strongly committed and dedicated police officer, leading the RUC through some of the most demanding, difficult and dangerous years.

“His battle in his final years with Alzheimer’s was fought with courage and fortitude. For his wife Sylvia and his family his loss will be sharply felt.

“At this time, I extend my deepest sympathies to his family and all those in whom he commanded deep respect.”

Mr Robinson continued: “At this very sad time our hearts go out to our parliamentary colleague Sylvia Hermon and her two sons. We know Jack had been battling Alzheimer’s Disease for a long time. He faced this terrible disease with bravery and stoicism.

“Jack Hermon was the Chief Constable of the RUC at a very difficult time in Northern Ireland’s history. We know his passing will be a major loss to Sylvia, her sons and the family circle.

“At this time we assure them that our thoughts and prayers are with them.”

Former Secretary of State Peter Hain said: “My sympathies go to Sylvia and the family. Sylvia has had a traumatic and tough time over these last years caring and coping and has shown enormous bravery and endurance.”

Sir John joined the ranks of the RUC in 1951, rising to the rank of Chief Constable by 1980, a position he held for almost a decade.

By 1989, when he was succeeded by Sir Hugh Annesley, he had overseen policing during one of the most turbulent periods of the Troubles, including the 1981 republican hunger strikes and inquiries into the infamous shoot-to- kill allegations made against the RUC in 1982, when six republicans were killed by a police unit.

He clashed with his Irish counterpart, Commissioner Laurence Wren, over crossborder co-operation and often criticised what he felt was a lack of operational assistance from Dublin Castle at the height of the IRA and INLA terrorist campaigns.

He married Sylvia Hermon following the death of his first wife from cancer. The couple have two teenage boys, but for the last six years Mr Hermon has been suffering from Alzheimer's, and in recent months was staying in a care home because he needed round-the-clock care.

During this time, Sir John had to be moved from his nursing home because of a potential threat to his life from dissident republicans who, according to security sources, had discovered where he was receiving care.

After retiring, at the time of the reforms led by Chris Patten which lead to the creation of the Police Service of Northern Ireland, Sir John warned it was not the time for fundamental changes.

He joined a platform party at an Ulster Hall rally to insist the report must not be pushed through without real political progress being achieved.