John McCarthy came briefly to national prominence in 1981 when, as Governor of Wormwood Scrubs, he wrote an open letter to The Times about the inadequacies of the steps being taken to reduce the prison population. His description of himself as the manager of a large “penal dustbin” captured the headlines.

He wrote: “From my personal point of view I did not join the Prison Service to manage overcrowded cattle pens, nor did I join to run a prison where the interests of the individuals have to be sacrificed continually to the interests of the institution, nor did I join to be a member of a service where the staff that I admire are forced to run a society that debases.”

He did not anticipate the furore that his letter would cause, and it came as little surprise when, a year later, he decided to leave the Prison Service and apply his talents to other fields.

His departure left the Prison Service the poorer. He had shown quite exceptional ability some years earlier in turning around Cardiff Prison, which had been suffering from very poor industrial relations and which, shortly before he took over, had experienced the first full strike of officers in the history of the Prison Service.

His approach to management rejected the notions of discipline and hierarchical leadership learned in the Army in favour of a more democratic, participative management style.

At Cardiff this change in approach produced dramatic results, as he conveyed to his staff his belief in the importance of trust while expecting outstanding performance. While his methods may not sound unusual today, his devolvement of decision-making to work- based groups was then revolutionary in the Prison Service, as was his insistence on a monthly staff meeting without a fixed agenda. The results were impressive, with morale, industrial relations and performance all improving dramatically, resulting in much higher standards of prisoner care. McCarthy won widespread admiration for what he achieved and the rare accolade of a visit from the Prince of Wales.

Wormwood Scrubs, though, presented a much more difficult, far larger and more complex task — especially as the prison had recently suffered a serious riot. He made a great effort to change the prison, but his impact was limited. Among the more interesting moments of his governorship was a visit from Mother Teresa of Calcutta, perhaps the only time she visited an English jail.

To many who knew and worked with him, McCarthy remained something of an enigma. Idealistic and likeable, he was a person of great integrity, yet sometimes he appeared to misjudge what was achievable. Faced with a problem he would seek the right answer, not the obvious one. A principled ideas man, he had a strong but sometimes austere personality. Rigorous in his approach to management, he could be a stern taskmaster. He suffered from a speech impediment, and it was a measure of his determination that he overcame this to govern Britain’s largest prison.

Born in London, McCarthy was the son of a naval architect. He was educated at Bedford College and Sandhurst, and joined the Bedfordshire and Hertfordshire Regiment, seeing service in Greece and Egypt. After attaining the rank of captain he decided to change career and applied to be an assistant governor in the Prison Service.

He was accepted in 1957 and posted to Feltham Borstal. At Grendon Underwood psychiatric hospital he learnt much about the power of group work, which greatly influenced his approach to management. In 1967 he was given his first command, on promotion to Governor Class 3 at Latchmere House Detention Centre.

He was awarded a Simon Fellowship and took charge of Dorchester Prison, achieving Governor Class 2 and a move to assistant director at South West regional office, where he supervised all the young offender establishments.

He took charge of Cardiff from 1976, and was promoted to Governor Class 1 at Wormwood Scrubs in 1980.

After leaving the Prison Service, McCarthy joined the Richmond Fellowship, a charity offering support for those with mental health difficulties. He worked there for some ten years as associate director and head of residential services.

He is survived by his wife, Julie Holborn, whom he married in 1982, and by two daughters from his first marriage to Gabrielle Robertson.

John McCarthy, prison governor, was born on November 21, 1928. He died on November 13, 2003, aged 74.