I flinch a little bit when, a few minutes after we meet, Steve Bell shouts "you stupid bastard!" at his cable box. He wants to get Gordon Brown's Chilcot testimony on screen but the controller is missing and stabbing at the buttons on the box he's berating doesn't seem to be doing the trick. I watch him, tall and sturdy with a mane-like beard, as he animatedly searches through the piles of stuff around his studio, talking unreservedly about the shortcomings of the cable box and doing impressions of Gordon Brown mumbling about the war.

"It's a shame everything's so neatly organised, but the TV controller has disappeared right when you need it," I joke. Fortunately he laughs. It would be hard for him to take offence, parts of his studio aren't a far cry from Francis Bacon's. Piles of newspapers and notebooks clutter corners, books and bits and pieces occupy shelves at hazardous angles, paint pots and brushes jostle for breathing space on the desk. Bell works almost entirely from this little extension on the back of his Brighton home, daily sending cartoons to the Guardian's offices in King's Cross.

It has been more than thirty years now since he left his post in a secondary school art department to have a go at cartooning, and more than a quarter of a century since his work first appeared on the back page of the Guardian. Before and during that time he has contributed to many other publications, including Time Out, NME and the New Statesman. He has been named among the 50 funniest acts in Britain by the Observer in 2003, and won numerous awards, including Press Gazette Cartoonist of the Year 2004 and Cartoonist Club Humorous Strip Cartoon of the Year 1984 and 1985. The strip, called 'If' (like the poem, he says), first appeared in the Guardian in 1981 and continues to this day, now along with a larger piece on the op-ed page that has run since 1990. With this op-ed cartoon Bell has created some iconic versions of the world’s most famous politicians: John Major as a useless superhero sporting Y-fronts over his suit; Tony Blair as a wild-eyed maniac (a characteristic he shares, tellingly, with Bell's Thatcher); and George Bush as a buffoonish, pouting Chimpanzee. With his strip cartoon he has created an altogether more surreal world of images, populated by as many penguins as politicians.

Bell studied fine art at university, but didn't get on particularly well with painting. Inspired by the likes of Ronald Searle and Robert Crumb, he drew cartoons for his own amusement, and later for film society posters at university, but left with no concrete ambition of doing it for a living. Instead he trained as a teacher and began teaching art. Teaching wasn't, however, a profession Bell took to easily or particularly enjoyed. "I was phenomenally bad at it. When you teach you have to be on the ball, all the time, every day. After a year’s teaching I thought 'sod this' and that's when I resolved to start cartooning for a living."

An avid reader of the Beano and the Beazer as a child, he sent some of his work to publishers DC Thomson, but got a rejection letter, "with the Beano header!". He still has it "in the files somewhere", he says wistfully. "I still treasure that."

Undeterred, Bell took some of his work in person to IPC, who were publishing similar cartoons at the time. "I went to see this bloke and he was quite off-putting at first and he looked at my stuff, which was a bit like Robert Crumb's, alternative, and a bit undergroundy, and he said 'look, you've got to realise, our average readership is about eight'." He laughs riotously, infectiously at the memory.

He still gets the Beano, out of a professional interest, he says. "And it comes with these astonishingly violent free gifts!" He laughs again and it's impossible not to be carried along by his loud chortle. I get the impression that, were I not here, he wouldn’t be any less animated: "Well that’s the good thing you see, I can shout back at the radio, and the television. I have to be able to talk to myself, that is a very important part of the process, so it’s great that no one is around."

The famous cartoonist Robert Crumb once said, in an interview with Bell: "Cartooning is a lonely job." Bell disagrees when I remind him, says it is solitary but not necessarily lonely: "It would be lonely if I didn’t enjoy it, but I work much better on my own. Besides, I have Gordon Brown, on the television and the radio to keep me company!"

He works almost entirely from home, venturing up to the Guardian’s offices in King’s Cross only when absolutely necessary. By today’s standards, the process of getting his artwork into print when he started working for the paper seems ludicrous, travelling as it did across the country by taxi and train. A cartoon had to be submitted a full week before it appeared in print. With the advent of the fax machine (he spent "a huge amount of money" on one in 1990) that all changed, suddenly deadlines were the day before publication.

Still arranged around the desk as we talk are roughs from the previous day, images recognisable from the morning's cartoon. He shows me his sketch book, the place where the process begins. Each page is numbered to reflect its position in the history of his work with the Guardian. Today's piece on Gordon Brown, which he begins in front of me, will be his 6535th op-ed cartoon when it appears in tomorrow's paper. This strict numbering is at odds with pages as chaotic as the room around us. Bell works excitedly, quickly reproducing an exaggerated image of Brown's bulk and many-chinned face with a black fountain pen.

Watching him sketch out this wholly unappealing vision of the prime minister, I'm curious about the strange relationship between the cartoonist and the figures he attacks from a distance. "There is such a thing as a cruel drawing," Crumb also said in that interview with Bell. I wonder if the Guardian cartoonist has ever had second thoughts about a particularly stinging attack, but he shows no regret: "You have to accept that you're going to piss people off, and you have to accept that this is a very offensive medium and you have to be offensive."

Neither is he nostalgic, he doesn't miss those he has characatured day in, day out once they've taken a back seat on the world stage. "There's always fresh blood isn't there?" he replies without thinking for very long. A well-heeled leftist, he certainly has fresh blood in the form of David Cameron. Unlike the heavy, hulking mass that he sees in Brown, he looks right through Cameron. The Conservative leader began life in Bell's world of images as a jellyfish but has since morphed into a condom, as if the cartoonist had looked to some stretch of dirty tide water for inspiration. It is instead the transparent, vacuous quality shared by the jellyfish and the condom that attached them to the Tory leader in Bell's imagination. He beams with enthusiasm at the memory of hitting on the idea, a particularly ludicrous way of parodying the political transparency Cameron is trumpeting from the rooftops.

Brown's bulk isn't intended to mark him out as a man of political substance particularly, but Cameron's condom is certainly intended to expose a lack of it. The tagline on a cartoon about the Lord Ashcroft scandal last year, "the non-dom in the condom", was an undoubtedly happy by-product of the idea.

Occasionally a politician on the receiving end of one of Bell's volleys of fire crosses the no-man's land between them to air a grievance in person. Hugh Selwyn Gummerly wrote him a letter complaining about "being dragged into my sordid fantasies or something". John Prescott said he'd like to punch Bell in the face - although not to his face. Far from a worry, this is the kind of thing that makes it all worthwhile, he says. "It's like an accolade. Bingo! They're supposed to hate it. The worst thing is when they say 'oh I'd really like that, can I buy it?' – it does happen. But, fuck off…"

Bell is a very amiable man, it is difficult not to think of that old expression, 'gentle giant', when trying to describe him. But the simmering vitriol in his cartoons sometimes bubbles up to the surface in conversation. He speaks seriously and passionately when we talk about the rights of younger, less established journalists.

"If you've been [at the Guardian] a long time you tend to get treated better, but people just coming in tend to get shafted and get crap conditions. There's a rights grab that goes on, and it happens across all papers, not least the Guardian but everywhere else too, and it is important to know what to ask for. It is a mean, shark-filled world out there and they are happy to have people working for nothing. 'Oh we pay nothing' – 'Oh nothing, oh well that is fine for me sure, OK, oh hold on how am I going to eat?' – 'Oh don't worry about food…' "

He laughs as he acts out this little pantomime, but there is more than a trace of anger in his voice.

"They'll rip off your rights as soon as look at you, it's been that way since time immemorial. These large media organisations are the worst offenders, they pay you once and that's it. It's like giving them a freehold on your house for one week's rent. It's so rotten, so stinking." He is not reserved about speaking out against the Guardian, who he accuses of "being remarkably silly" and "spending money like a drunk with three arms".

"They moved into this massively expensive place and fitted it out in the most luxurious manner, and they've got media studios galore just sitting there unused and it is just tragic." Bell sits on the board of the Guardian's National Union of Journalists (NUJ) chapel, and last year was involved in a dispute between Guardian photographers and the newspaper, attacking proposed changes to the photographers' rights. He speaks fervently about the treatment of trade unions across the board.

"The thing that angers me the most is that the trade union movement, which the Labour party is actually an expression of, never gets a fair ride (…) Its rotten and stinking and I hate it. I think it's a terribly bad idea that the trade union movement gets such a shit ride, any strike, any dispute, its always 100 per cent from the managers point of view."

"There's not much left of the left," he adds wearily.

"This is how I've always felt, lurking down here in my Brighton pit. In many ways I'm very glad to be away from it all."

Do you ever feel the need to hold back from letting your own political views influence your choice of subject matter?

"No. It only makes any sense if you have an angle of your own, and I very freely admit I do have an angle of my own. I've got my own opinions about the world and the way it goes on and that is what feeds what I do. You might say its propagandising or something but, too bad, tough crap, we live in a world that is flooded with propaganda, and you have to fight it both ways.

"You can't hold back and be Olympian about it, and say, 'oh well, the big picture is this and this…' No, the big picture is made up of all the little pictures, and you have to have your own view."

I ask him if he has any thoughts about hanging up his boots, if he might end up too weary of it all to bring himself to satirise politics in years to come. Or does the prospect of a new Tory government spur him on?

"There's never going to be a government that believes everything I believe, so there will always be a reason for hammering on. Well, as long as they'll have me, it's in the lap of the Gods I guess, well, the editor anyway."

He laughs again, another resounding chuckle, cynical and delightful. But then Bell seems to find sheer delight in his cynicism, and in amongst the moments of seriousness, of anger and dismay, there is real amusement at the folly of politicians, paper editors and Gods alike. I get the impression that it is this wickedly funny streak that saves him from it all, and that it will keep him going for a while yet.

Steve Bell now has his own website, www.belltoons.co.uk, where you can view extensive archives, license images and follow his blog.

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