But now the creator of the character, Oxford author Colin Dexter, has hinted that it could be coming to an end.
Next week the sixth series of Lewis, the spin-off show from Inspector Morse, will be screened on ITV1.
Mr Dexter, 81, told The Radio Times: “I don’t think he can go on much longer.
“They’ll probably do one more series. The first two were ridiculously complex. They’ve got better.”
Kevin Whately, who originally starred as sidekick to Inspector Morse before taking the lead role in Lewis in 2006, told the Oxford Mail in 2010 that he believed it could soon be time to pension off the police officer as he reached police retirement age.
In all, 33 episodes of Inspector Morse were filmed between 1987 and 2000.
The sixth series of Lewis will bring the number of episodes of the spin-off drama to 24, and Mr Whately has said he would not want to do it for as long as Morse.
But another spin-off prequel, Endeavour, starring Shaun Evans as the young Morse has now been commissioned for a second series.
Mr Dexter said: “One reason Endeavour did well is because everyone could understand it.
“People said to me ‘Brilliant, typical Dexter’.
“Well, I didn’t write it. I wish I had.”
Inspector Morse, Lewis and Endeavour have brought thousands of visitors to the city.
Colin Cook, Oxford City Council cabinet member for development, said the impact on tourism had been “significant”.
He said: “It was a contributor to introducing Oxford to not only a national but an international audience and is a factor in bringing visitors to the city.
“Aside from all the money the film companies themselves spend here, the work they have done over the years has been enormously positive in terms of the image projected of Oxford – putting aside the murder rate in the programmes being 10 times what it actually is.”
He said it would be disappointing if the series finished.
But he added: “I have heard before that the last series was going to be the last series. But sure enough, another one pops up. It will be sad if it does end, but it’s better to end on a high than go the way of some series where they milk it for all they’re worth and end up delivering rehashes of previous stories.”
Scenes from the new series, which starts on Wednesday, May 16, at 9pm, were filmed at The Punter in Osney Island.
Landlord Tom Rainey said: “Personally I love Lewis and I would love to see it continue but it has been going on a long time. To have Lewis filming in the pub was great.”
ITV spokesman Kate Richards said: “ITV are in discussion about more episodes of Lewis but we don’t have any further news on it yet.”