Paul Simpson, who died a few days short of his 67th birthday, was director of finance and information technology in the Down Lisburn Trust when it was established in 1994, going on to become its chief executive.
He was recognised as an accountant, strategist, organiser and manager and, for 17 years, had an influence in the provision of health and social care in the Downpatrick and Lisburn areas.
"Paul believed working in the Health Service was a serious business, but you didn't have to be serious all the time," said friend and former colleague, Paul McBrearty.
"He had a calmness that reflected his control of situations and he excelled at getting the best out of people."
Paul Simpson was involved for 20 years with Threshold, a voluntary mental health agency providing services to people of all ages.
He played a major role in helping to build the body up to the position it occupies today and be became its chairman. He was also chairman of Victim Support.
He relaxed by exploring Ireland with his wife Pat and family and they holidayed at Rathmullan in Donegal and Corkmacsherry in Co Cork, where they rented a cottage for 14 years.
In his youth Paul - a native of Belfast and an old boy of Campbell College - played cricket for Derriaghy and was captain of the Civil Service team. He was also a hockey umpire.
He was a member of the Folio Society, an organisation dedicated to producing books affordable to everyone.
Paul is survived by Pat, to whom he was married for 43 years, and their sons Richard and Michael, and by his 93-year-old father.