The fountain, of course, is what everyone remembers, where everyone comes first, and we're surprised there hasn't been a bit of timely plumbing. But then, La Treille takes its role as Provence's most famous village with a negligent detachment. Nowhere can you see the name of Pagnol. There are no shops, no souvenirs, no longer a cafe. There is not even - be warned - a public lavatory.
It's not that the residents wish you hadn't come. It's just that they're still a real community. In the shade of the plane trees outside the Republican Club, the men of the village still gather to play boules as they might have done in Manon's time. And, with true rural hospitality, twice while we're there ladies come to their doors to ask whether we need water.
There's a bus park today at the bottom of the hill, and a few commuter villas that make rich targets for burglars from Marseilles. But the village remains much as Pagnol pictured it in the opening paragraphs of Jean de Florette: under terracotta tiles huddled among cobbled squares and alleyways, sheltering from the sun and the bite of the mistral. The single road soon peters out into the high garrigue, the wild Provencal countryside that is woven into all his books and films. The literary geography of few other writers can correspond so closely with that of their life.
Marcel Pagnol was born in Aubagne, the bustling little market town just down the hill. Totally Provencal, cheerfully unglamorous, it is famous for its santons - ceramic figurines - and for being the headquarters of the French Foreign Legion. And although Marcel was only two when his schoolmaster father transferred the family the dozen miles to Marseilles, Aubagne sees itself increasingly as the gateway to Pagnol land. The tourist office gets an average of 100 inquiries a day, from places as distant as China and Japan.
A few steps along the boulevard, The Little World of Pagnol is on its way to becoming the town's principal attraction. As well as memorabilia, it boasts an animated diorama of those ceramic figurines whose faces unmistakably belong to Yves Montand and Gerard Depardieu - those stars of the Claude Berri films. Though crowded with school kids, it proves less tacky than we fear. And, as with much else in Aubagne, we can't grumble at the cost - entrance is free.
But up behind La Treille, between the triangle of limestone peaks forming the Massif de l'Etoile, the real Pagnol's Provence exists virtually unchanged. Carpeted with rosemary, lavender, thyme, it's so exactly like the books and films that it looks delightfully familiar. A map from the tourist office shows the directions, but we find that the best guidebooks are the autobiographies that let Pagnol himself bring it all to life.
La Bastide Neuve is the old farmhouse of his childhood summer holidays that was his lifelong idea of heaven on earth. He was later to make it the home of Jean de Florette. ("Look!" cried the hunchback. "Just see those giant brambles, that tangle of olive trees, bushes of rosemary! It's like Zola's paradise. It's more beautiful than paradise!")
Overgrown with clematis, the place still has a vaguely ramshackle look, though peering over from the olive grove we discover a new swimming-pool in the back yard. Then comes the garrigue, dense with aromatic herbs, cut by deep ravines. And somewhere it's all up there: Manon's cave, the hidden springs, the Vallon of Passetemps where Marcel's father won his glory, the cave of Grosibou on the summit of Taoume where Marcel and Lili, the peasant boy who taught him the secrets of the hills, met the fearsome eagle owl while sheltering from a storm.
We have the wild landscape to ourselves. The only sounds in the hot silence are the chirping of cicadas and the drone of insects. But as we struggle to the summit of La Grande Tete Rouge, long before we see him we catch the animated oratory of M Louis del Rosso. He is not only, he tells us, the best Pagnol Country guide; he's also the president of the Pagnol Association. He is leading two Swiss tourists, who are getting as much fun from his ebullient eccentricity as from their guided tour itself.
From our windy eyrie, two kilometres above a pocket-sized Marseilles, M del Rosso points out the sites of Pagnol's life. He ought to know. He says he worked as an extra in the films. In the following days, wherever we go, in caves, in lonely vallons, we seem fated to meet M Louis. Although he has no English, his exuberance alone must be well worth his fee.
Occasionally you meet other bands of Pagnol pilgrims, but the atmospheric landscape hides a hundred secret places. Among the herbs and the wild flowers, there is sometimes a sense of walking with ghosts. On a bare stretch of garrigue we come upon a ruined hut, haunted by Marcel's younger brother Paul. While Marcel's love of the hills made him a writer Paul fulfilled his by becoming a goatherd, living in this hut with his harmonica for company. Now only the foundations remain, with wild roses growing among the rubble. He died at 34 from a tumour of the brain - another heartbreak for Marcel, who felt the force of destiny, cruel and benign, so often in his life. Paul was almost certainly his model for Manon.
Pagnol now lies in the little cemetery just down the hill from the famous open aqueduct that flows through the book and film of My Mother's Chateau. There are many flowers on the grave, and we read a note written in English: "Thank you, Marcel, for the joy that you gave us." I've brought a few carnations. That seems the most appropriate. But my wife's been picking wild flowers from the hills. She thought he'd like those best.
EasyJet (0990 292929) has flights from Luton and Liverpool to Nice starting at pounds 98 return, but as the summer peak and World Cup approach seats at this price are scarce. The most reliable economical choice is to use Eurostar (0345 303030) from London Waterloo, changing at Paris or Lille for a direct service to Avignon. The journey time is about nine hours, and the fare is pounds 119 return.
The French Travel Centre in the UK is at 178 Piccadilly, London W1V 0AL (0891 244123, a premium-rate number). The Cadogan Guide to Provence (pounds 14.99) is handy.