So he jumped at the chance of making a celebrity guest appearance in the long-running radio series The Archers.
Mr Dexter, 79, from North Oxford, has been an ardent fan of the BBC Radio 4 series since it started in 1950.
He said: “I remember first listening to the show when I was a trainee teacher in the early 1950s.
“I seldom miss an episode so I was delighted when I was asked to make an appearance as a celebrity guest, opening the annual village fete.
“I travelled on the train to Birmingham about a month ago and recorded four or five little interludes.
“The episode went out on Sunday and I made sure I tuned in.
“I have appeared many times in different things, but seldom in such distinguished company.
“The Archers still gets millions of listeners.
“You get to know the characters awfully well and the storylines are always very interesting.”
Mr Dexter said he gained a reputation as an Archers fan after making sure that his most famous creation, Inspector Morse, was a fan too.
The writer – who has made cameo appearances in episodes of Inspector Morse and the spin-off series Lewis – said: “I made sure Morse followed The Archers and would create scenes where Lewis would come in and interrupt him when he was listening to the show.”
He added: “Over the years I have met members of the cast, including Norman Painting, who played Phil Archer for many years.
“A few months ago, I attended Mr Painting’s memorial service in London.
“I used to be the chairman of the Oxford Book Association and, because of my interest in The Archers, Norman came to talk to our members on a couple of occasions.
“He was an honorary fellow at Christ Church and very well known.
“I’m not the first celebrity guest to appear on The Archers – they even had Princess Margaret on once.
“Once a year they get a celebrity to open the village fete and this time it was my turn. I thoroughly enjoyed it but I don’t think I will be on again – it was a one-off.”
Vanessa Whitburn, editor of The Archers, said it was a delight having Mr Dexter on the programme.
She said: “Inspector Morse has always been a fan of The Archers, as has his creator.
“It was great to return the compliment and have Colin present the prize for solving the murder mystery at the Ambridge fete.”
Other celebrities to have made a guest appearance on The Archers include Sir Terry Wogan, Dame Judi Dench, Alan Titchmarsh, Griff Rhys Jones and Chris Moyles.
Mr Painting, 85, from Warmington, near Banbury, played the part of Phil Archer for almost 60 years until his death last year.
- Mr Dexter’s appearance will be repeated in Sunday’s Archers omnibus edition at 10am on Radio 4