This is someone who although he didn’t host a lot of game shows, he definitely became a well-known figure in that area. William G Stewart (the “G” stands for Gladstone) had a career in TV that lasted for over 40 years. He started out working behind the scenes of various shows, and he went on to be the producer and director of some 60s and 70s sitcoms, arguably the most famous of these was Bless This House (he also contributed to some documentaries on what it was like to work with Sid James).
By the early-80s he went on to work in game shows, including Family Fortunes and The Price Is Right, where he made sure that even if people hadn’t been invited to “come on down”, they still all had a good time. By the late-80s, his production company were commissioned to produce Channel 4’s new daytime game show Fifteen-To-One. Not being sure who should be the host, he decided to go in front of the camera himself.
Fifteen-To-One was of course the game show where contestants were challenged to show off their general knowledge, and were eliminated until one remained. He was also on the team of writers, usually contributing questions on the subjects of history and politics. As the years progressed, the show began to develop its style, and became known for doing things such as giving away antiques as the prizes. By the early-90s, the show was popular enough for there to be a celebrity edition.

He then went on to host Famous People, Famous Places… on ITV (and this was later repeated on Channel 4), but this lasted for only two weeks, and is mostly forgotten now. Fifteen-To-One had now settled into being an daytime game show that was as popular as the long-running Countdown, and he also hosted a special edition when Richard Whiteley and Carol Vorderman were the contestants.

Going into the 2000s, Fifteen-To-One was at the point where a group of contestants regularly made the grand final with rather high scores, and some felt that there were now too many “proper” quizzers taking part. When the show did finally come to an end after 16 years, there had been over 2,000 editions, and by this point he was regarded as one of the best hosts around, always making sure that people maintained a good standard.

There was only ever one scandal that put the show’s reputation at risk, when a series champion was stripped of his trophy for bending the eligibility rules. After this, Stewart just about retired from TV, although he did also contribute to Celebrity Mastermind and The People’s Quiz (but he was turned down by Strictly Come Dancing). Although he probably didn’t expect it to happen when he started out, he became a much respected person in game show circles.