Snow lies over Suffolk as I write, and headlines gloom economic stringency. But I am looking at a cartoon of March 1947: a flint Suffolk farm under heavier snow and a man under a broken Land Rover, watched by a contemptuous cat. Out of the window leans a muffled wife saying “It's for you dear. The Editor wants to know when the something or other he's going to get a cartoon?”

It is, of course, the great Giles, star of the old Daily Express, who even in pre-digital days steadfastly refused to work in London. He frequently got snowed up on his pig farm in those chilly postwar years, struggling to get his intricate, perfectionist cartoons on to the four o'clock train from Ipswich in the care of the guard. It is said that they once sent a helicopter: Giles was that important to the paper, and indeed to national morale. He remained beloved for the next half-century and in millennium year was posthumously voted Britain's favourite cartoonist - and his baleful, fox-furred Grandma the favourite character. His life and characters are being celebrated in a wonderful exhibition of originals and biographical notes at the Cartoon Museum in London.

So when you grow tired of piffling celebrity, mealy-mouthed nannyism, alarmist pessimism and economic whining, go there for an antidote. Or pick up an old Giles album. Although his drawings are fascinating footnotes to social history, that is not the point. He should speak to us now: this boy who left school at 13 in the hungry Thirties and by 20 was blind in one eye and deaf in one ear after an accident. He offers a lesson in humanity, gaiety, generosity, perfectionist hard work, healthy grumpiness and the need to raise two fingers to the jobsworth in the peaked hat. Where is Giles now, when we need him to jeer at ID cards, council snoopers and curriculum authorities? Who shall update Auntie Vera's sniffles into 21st-century health neuroses, or deploy a malevolent Grandma and evil children in a commentary on hate-crime and all the -isms?

Giles never sold originals - rejecting the “raucous cry of the market” - and gave much work free to charities. He left two lorryloads of artwork to a trust now based at Kent University, which shows them online on cartoons.ac.uk. The exhibition in London picks out 80, with biographical detail that inspires almost as much admiration. Moving to the right-wing Express bothered him (“They bribed me... stuck a cigar in my face and told me what was to be”) but his irreverent stance was unchanged by its editorial line or indeed its moral one: he was forever introducing a mutilated Rupert Bear in the background, and putting bulges in trousers that the prim subs had to blank out.

He distrusted Churchill, who in return disliked his work even when he was a powerful morale-booster during the Blitz. Perhaps his humane cynicism about high-flown rhetoric stung the war leader: Giles was in the Home Guard and saw domestic destruction close-up, and in drawing his unheroic soldiers followed the tradition of Bruce Bairnsfather in the first war, observing that squaddie humour still worked: “mud, cussing, lorries that won't go, shells that fall too near and boots that pinch too tight...” Who can forget the soldier looking up at an approaching missile and observing: “Oh look, here comes your Easter Egg.” Or the GI bride taken home with a baby, but horrified to find that her Wally lives not in a skyscraper but a hillbilly shack?

In 1944 he was a correspondent at Arnhem; he drew pictures of cells and gallows at Breendonck transit camp, and went into Belsen with the liberators. But here he flatly refused to draw, saying that photographs alone must tell the story that 50 years later was still to “haunt and horrify” him. Yet out of this grew the warmth and gaiety of Giles's postwar work. His Britons - stumpy, impudent, longsuffering, domestic, anti-authoritarian - cluster in the Giles Family, at whose head stands the baleful circular black figure of Grandma, a mouthpiece for every bracingly incorrect view: a fan of Lenin, hanger and flogger, hedonistic gambler and drinker, keen on violence. She smells of embrocation and mothballs yet is beadily on the ball.

She links the postwar tribe with its history: her mother “helped wash up at a Fete attended by Queen Victoria”. On a Christmas album we find her playing poker with an equally grumpy Santa in her nightie, while his presents go undelivered.

Giles's story - and especially Grandma - make me think of Yeats's poem Lapis Lazuli, which defies the fall of civilisations and the height of human tragedy to affirm that “all things fall and are built again”, and that it is a spirit of gaiety that builds them. He refuses the ancient Chinese sages on the carvings a melancholy tune: as they play, “Their eyes mid many wrinkles, their eyes/ Their ancient, glittering eyes, are gay”.

I am not ancient yet, but in Giles's honour last Wednesday night at the Cartoon Awards dinner I not only dressed up as Grandma in an eBay fox-fur and terrible dead-bird hat, but by low cunning, the stealthy acquisition of a second fur and the artful customising of a straw hat with car paint and fake pheasant, I inveigled that cartoon aficionado and Cartooon Art Trust founder Lord Baker of Dorking to do the same. He showed reluctance at first, but once he got the fur on seemed strangely loath to lose it. Grandma, after all, has more natural authority than most politicians can dream of.

A career can only have one zenith and this was mine: being a twin Giles Grandma with a former Tory Home Secretary. It's all downhill from now on. Even Kenneth Baker's fox fur was so overcome by the event that two of its horrible paws fell off. I feel that Giles would have approved.

Giles - One of the Family is at the Cartoon Museum (020-7580 8155) in London until February 15, 2009

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