1984 was an interesting year. Spandau Ballet was the biggest band in the UK. Big Brother was still 16 years away. I had been freelance for six months and was surprised to find I could still afford to eat. And a small, single column cartoon appeared on the front page of The Westmorland Gazette, the UK's top regional weekly newspaper.

Okay, I exaggerate. Madonna was much bigger than the Kemp brothers. But the cartoon was a new departure and I'm mildly astonished to find it continuing to sit on the front page, twenty five years later.

It's sobering to reflect that the cartoon is now older than some of the Gazette's reporters. A colour version always appears online, so it's staying fairly hip and trendy. It can even be viewed on an iPhone. It has yet to Twitter, Digg or Spotify but a variation appears on the radio, it's been on TV and even inspired a theatre set.

Looking back, you can see that the drawing style has changed dramatically. This is partly due to the deadline. In the old days, I took a day to do the cartoon. Now I get three hours from seeing the story to finished artwork. That includes at least four preliminary sketches for the editor to choose from - if he hates all of them, it can be up to ten). And the cartoon is no longer painstakingly inked, photographed and converted to metal plate. It is scanned into a computer, tinted in Photoshop and sent down the internet to Blackburn in a little under twice the time.

Worryingly, some of the jokes are similar. This week's, for example, is about Sellafield. I've been 'doing' Sellafield for almost the entire career of the Gazette cartoon. Other recurring topics include Windermere power boats, low flying aircraft, Kendal's bewildering traffic system, second homes (grrr) and the local hospital. When I began, the Gazette's editor had me campaigning to have the hospital built. Fast forward 25 years and the cartoon is campaigning to prevent it being closed.

There have been some exciting highlights. One cartoon drew weeks of angry correspondence, beginning with someone ringing up and threatening to horsewhip the editor. (He was quite proud of this and when he retired, I gave him the original.) A neighbour of mine wrote in such strong terms the paper couldn't publish his letter, which began "I have never found any of Shelbourn's cartoons funny ...".

Editors like reaction and the cartoon remains one of the few places in the paper where an opinion can be trotted out. So I have been free to have a go at the Tories, Liberals, all the local councils, the National Park, the RAF (I'm still waiting for my free ride in a jet, btw), National Trust, the local skateboarding fraternity and grammar pedants county-wide. One of the dangers of sending up local organisations with silly suggestions is that they occasionally take you seriously and your daft idea crops up in the next set of minutes.

I still have most of the 1300 original cartoons and 5200 preliminary sketches. Occasionally originals get sold or given away to much-loved and highly valued friends (who promptly hang them in the loo). The rest are carefully filed away against the day when Tate Modern gives up on pretentious Brit Art installations and decides to have an exhibition of something more amusing (and, let's be frank, more baffling to anyone outside Cumbria).