Drummond Hunter was ''a big man'': in build, in spirit and in life. He was a creative, imaginative, always positive thinker, and an energetic campaigner. When he died, suddenly, he left a diary full of engagements and commitments to the many organisations with which he was connected.

His loss will be keenly felt over the coming months, with countless meetings and social occasions set to be deprived of a lively and engaging presence, and a vigorous contributor. Equally, the letters pages of so many newspapers and publications will not seem the same without their regular missives signed either by T D or Drummond Hunter.

But the greatest sense of loss will be felt by his family and his friends. This was hardly an exclusive club. He was, above all, a humanitarian, believing sincerely and deeply in, as he might have put it, the infinite potential of people. ''There are no strangers,'' he would often say, ''only friends who we haven't yet met''.

Drummond Hunter was born in Cumnock in 1918, one of eight children. He shone academically and was offered a scholarship to George Watson's, in Edinburgh, where he became joint dux in 1936. Another scholarship followed, this time to Oxford University, but he was reluctant to place a financial burden on his family and felt unable to take his place at Balliol College.

Instead he chose Edinburgh, where he studied history and law, until his university career was interrupted by the outbreak of war. After serving in the OTC Glencorse, he travelled to Hong Kong with the Royal Scots in 1939.

In a remarkable life, it was this time in Hong Kong that would provide the most formative of experiences. In the summer of 1941, he first met his future wife, Peggie.

In December, when the Japanese attacked Hong Kong with overwhelming force, Drummond was wounded and reunited with Peggie, a volunteer nurse at the British Military Hospital. Then, on December 24, while being transferred to another hospital, he suffered a broken back when his ambulance crashed during an air raid. Again, he was reunited with Peggie, and on Christmas Day, 1941, an hour after the surrender to the Japanese, the couple were married in a ceremony witnessed by five people and celebrated with some Christmas cake and the only bottle of champagne in the hospital.

But their hopes that marriage might keep them together were in vain. As prisoners of war they spent three years apart. Drummond was held in the Shanshuipo internment camp, an ordeal that took an obvious physical toll, his 6ft 4ins frame reduced to just eight stone.

The experience also left a psychological mark, though he hardly ever spoke of his experiences as a PoW. He may reasonably have argued that the effects were positive, for he resolved not to be a passive member of society, but to set about actively changing it for the better. Until his death this fuelled a consuming desire to inspire institutional reform, most notably in hospitals and prisons, when he judged them to be inhumane, ineffective, and counter-productive.

Towards his Japanese captors, he felt no bitterness. Last month, on the TV series, The Real Tartan Army, he said: ''You have to forgive, because hatred corrodes you.''

Drummond and Peggie were reunited in 1945 and returned to Scotland, settling in Edinburgh, where Drummond was able to complete his law degree. He served his apprenticeship with Dundas and Wilson, then joined Blair and Cadell, before, in 1954, leaving the profession to become secretary and treasurer of the Royal Edinburgh Hospital Group.

There was a big job to be done, and his first priority was to improve living conditions for the patients and thus to restore their dignity. As a manager he was charismatic but kind, and a non-conformist, willing to take risks that could benefit the patients, and always challenging traditional hierarchical structures in this respect he has been called a ''responsible schemer'' believing in consensus management techniques that today are more widely accepted.

Typical of his unorthodox approach was his collaboration with well-known artists in establishing ''one of the finest art galleries in Edinburgh'' at the hospital. This was open to the public on several occasions each year. A former colleague recalled: ''The artists were happy (they sold a few paintings), members of the public began to see the hospital in a different light, and the hospital staff were encouraged by seeing the walls of prejudice begin to tumble.'' Using art, again, he occasionally opened the hospital as a concert and theatre venue, staging a controversial fringe production by Francis Warner.

In 1974 he left the Royal Edinburgh Hospital to become the first secretary to the Scottish Health Service Planning Council. Throughout his career in the NHS he thought and, unusually for a practising public service manager, published extensively and authoritatively on the organisation and management of the health service.

Present preoccupations with effective policy implementation, devolution of decision-making, and encouraging innovation were all issues Drummond Hunter felt passionately about as a senior NHS manager more than 40 years ago.

Then, in two decades of so-called retirement Drummond's impact on the voluntary sector was perhaps equally significant. He was an active member, invariably a leading light, in the Scottish Institute of Human Relations, Scottish Council on Disability, Sacro, Howard League for Penal Reform, Penumbra, the Child Psychotherapy Trust, the Sutherland Trust, and Art Extraordinaire.

He was also a trustee of the Rudolf Steiner School and an enthusiastic member of the Royal Scots Club and the Carlyle Society. Another cause he led in recent years was the struggle for ex-gratia payments for prisoners of war.

At the age of 80, he provided both the vision and driving force for the creation of the Scottish Consortium on Crime and Criminal Justice, bringing together the main voluntary groups and academics working in the youth and criminal justice fields.

To honour his contribution, the consortium has announced plans to establish an annual Drummond Hunter memorial lecture.

Beyond his sincere and deeply held beliefs and ideals, Drummond loved hearing and telling jokes and regaling his audience with a well-selected quotation or, indeed, some of his own recollections or wise words.

Always a rationalist, he was able to see the positive in any situation and he felt an affinity towards life's underdogs, as well as the desire to speak up on behalf of others.

He was a practical idealist, a thinker and a doer, or, as one former colleague put it, ''tall enough to have his head in the clouds, but always with his feet planted firmly on the ground.'' In 1998, seven months before Peggie's death, Drummond Hunter was awarded the OBE, for services to the community in Scotland.

He was devoted to his family and is survived by his children, Katherine, David, and Stephen, and eight grandchildren.

T Drummond Hunter OBE, born December 22, 1918, died April 13, 2002.