Then, after 13 years at ITN, in 1978 he more or less vanished from the television screens of Britain and the public had to find fresh household favourites who read and reported the news clearly and intelligently.
Mills's new job was with the Post Office as its first Head of Public Affairs, a role he continued when telecommunications was separated from the nationalised Post Office and he elected to serve in what became known, in 1981, as British Telecom. He was also promoted to be deputy director of corporate relations.
Mills missed the fun, excitement and camaraderie of the television news trade, but he had found a significant new sector in which to exercise his incisive use of language, his intelligence, his charm, his unflappability and his sense of style. He was thus poised alongside Peter Young, his director, to give Sir George Jefferson, chairman of the board, the support that was needed on a hazardous trail to what, in 1984, became the biggest act of privatisation the world had then seen.
Today the international reputation of the company, now known simply as BT, ranks high. The part played by Ivor Mills in helping to bring that about was crucial. He stood as very public evidence that the old Civil Service/nationalised industry era was at an end. He always acted as a man with a mission to inform with as much grace and skill as possible.
Educated at Stranmills College and Queen's University, Belfast, he had seemed destined for a career in music, having studied classical composition and musical history, becoming an LRAM and teaching for a while in Belfast. Instead, he was drawn into working as a journalist and then as a producer, editor and presenter of programmes - first for the BBC and Irish radio as well as for Ulster TV. While building up a curriculum vitae that would take him into Geoffrey Cox's team at ITN, he also worked for the World Service of the BBC and for Southern Television.
It was in 1965 that he achieved his ambition to work for ITN. He became a member of a new breed of "national figures", though he acknowledged that this was a kind of strange fame. He never took himself too seriously, but he approached his work with a high degree of professionalism.
As a reporter he covered a wide range of stories, including the sad thalidomide drug affair. Among those he interviewed were Margaret Thatcher, Freddie Laker on the launch of his airline, Harold Wilson, Sophia Loren, Robert Kennedy, George Brown on his (final) resignation, Dr Barnes Wallis (the inventor of the bouncing bomb), Sean Connery and the racing driver Graham Hill. In the mid-Seventies he conducted an eyeball-to-eyeball live interview with Jocelyn Stevens over an industrial dispute in Fleet Street - still recalled by broadcasting colleagues as a model of its kind.
Although a supporter of the rights of the Protestant majority in Northern Ireland Mills was totally free of bigotry and utterly opposed to violence of any kind. He boldly displayed these views when visiting Ireland as an ITN reporter, and it grieved him that the resultant personal threats from extremists on both sides curbed his excursions to his beloved Ulster for a number of years.
Both on the screen and off he was envied for the skill with which he could crack a joke, suggest a bit of tap-dancing or lift an eyebrow in a way that would banish nervousness (often masked as pomposity) from most occasions. When that failed, however, he could assume a daunting mien.
He was also a noted bon viveur, a keen exemplar of the extended lunch, and close pal of fellow broadcaster Reggie Bosanquet at whose tennis parties he was able to play an accomplished and stylish game.
For a while after leaving ITN his contract with the Post Office allowed him to undertake a limited number of freelance broadcasting contracts, but before long his task as Head of Public Affairs took up all his time. He had to build up a unit that would make this nationalised industry more capable of dealing with attention from Parliament, political parties, academic, CBI and other pressure groups and release some managers from timidity or ignorance about the fruitful conduct of public affairs.This was not too onerous for, as a freelance, he had already been training top Post Office people in television and radio interview techniques.
Other well-known broadcasters, also acting as freelances, took over Mills's former training role, but he remained available to tune up the appropriate board member or senior manager when a major television interview was imminent. In the event, most of the managers involved found the actual interview itself easier than the training bout with Ivor Mills.
He supervised BT's lobbying of members of both Houses of Parliament, ensuring that MPs and peers obtained full briefings on any aspect of telecommunications that interested them and sometimes on less obvious aspects of the industry that really needed their attention.
He still loved, of course, to be involved in the big television occasion - working closely with the Queen, for example, in preparation for the royal opening, through multi-video conference links, of the Anscam cable linking the United Kingdom to Australia via North America.
He was on parade, too, when BT was involved in the opening of the Hong Kong Stock Exchange. With some 2,000 guests assembled in Hong Kong and a three-way teleconference link to London about to open, Mills's autocue failed. It was time for an impromptu performance without notes or autocue.
After retiring from BT in 1988 he carried out consultancy work with, among others, Sunset & Vine, the television production company, until poor health, including the effects of suffering a hit-and-run accident outside his home in north London, curbed his activities. He would turn out in brave form at gatherings where he could meet former television or BT colleagues.
He married in 1956 Muriel Hay, also of Belfast, a concert pianist who is a now a distinguished private music teacher in London. Mills always acknowledged her superiority at the keyboard, though there was a time in the 1950s when they appeared together on television in piano duets in both Dublin and Belfast.
Ivor Mills, broadcaster and media executive: born Belfast 7 December 1929; married 1956 Muriel Hay (one son, one daughter; marriage dissolved 1987); died London 30 May 1996.