I wasn't sure exactly where the church had been, or if the chapel still survived; but while out cycling between Pont le Poitte and Doucier, I saw a sign to l'Ermitage Saint Sorlin pointing through Charézier village along the road to Lieffenan. I followed it. I wasn't sure what to expect; was this the chapel Lacroix had written about? I might have been headed for a modern retreat centre for all I knew. Another sign directed me beyond Lieffenan. Climbing steeply up from the valley of the Ain, I came to a forest track, and a third sign pointing up it.

I had no idea how far it might be. I was already late for lunch ten kilometres away, and so I merely stopped and gazed wistfully up the track, got back on, and cycled home.

The following day, I decided to go and find the hermitage. It was a brilliant late summer afternoon. I left my bike at the bottom of the track. I locked it, the first time I think I have ever done so in the Jura. I regretted doing this, but I had no idea how far I would be walking, and didn't particularly want to come back down out of the forest and find my bike gone.

The path cut across the top of a field, and then turned sharply up into the forest. Immediately, it began to climb,through close ranks of ancient oaks. The path was coated in acorns; occasional lizards scarpered out of the undergrowth, and once I heard something large leap off the pathway ahead of me into the bushes.

I kept a brisk pace. Soon, the path was cutting into the steep side of the hill; below to my right were the tops of trees, and above mossy rock outcrops gleamed through the thickets. The low afternoon sun sent bold shadow lines through the forest, the air filling with the chatter of birds coming home to roost.

At a dog-leg turn in the path, a sign reassured me that it was only another 300m. The path levelled out, and I could see the way I had come below me. I turned a corner, passed a small Marian shrine - and there it was ahead of me in the clearing, a narrow west front with a double bell turret above, only one bell in place.

The clearing was cool after the climb through the forest. A couple of rabbits kicked heel and scattered as I approached, but apart from them I might have been the only one on the mountain.

I had found Lacroix's Saint-Sorlin. The little chapel sits in the middle of a large rectangular wall, the outline of the original church. It has a roof of stone slabs in the local manner. The expanse to the west forms a kind of lawned garden, an entrance to the chapel, while to the east the shuttered chancel window opens onto what appears to be an abandoned archeological dig. There are no traces at all now of the dwellings Lacroix says existed on the slope to the south of the church.

I wandered back around to the entrance. The door was wedged open, and a sign says Priere de Laisser la Porte OUVERT! The threshold has a strange carving of a cow wrapping its tail around a pair of feet, but otherwise presents no serious barrier between the organic outer world and the sanctuary within. Above, a head looks down, and the inscription reads Martyr de Saint-Saturnin.

The sun was sinking into the forest, and its light made a golden mouth of the doorway. I stepped through it.

Inside, the space was square, cool and damp. Brick tiles spread around three large foliage medallions on the floor. Apart from these, a stone altar and two memorials were the only features. One of the stones recalls that the hermitage was built by a man called Joseph Simonin. He had been a farmer in the adjoining hamlet of Lieffenan, but felt called to establish the chapel here, which he did with his wife in 1834. They lived as a silent community, receiving pilgrims, until his wife died and he became a Holy Spirit Friar in the Auvergne. He died there in 1856, but in 1987 this little chapel was restored and his remains were brought here for reburial.

In 1980, Lacroix had bemoaned the state of the hermitage and feared for its future, but today it is a rejuvenated centre of energy. Fresh tulips decorate the stone which Simonin had set up to recall the great days of Saint-Sorlin's past. The stone, now broken, was recovered from the ruins in the 1980s at the time of the restoration. I signed the visitors book, noting quite how many visitors the chapel had, many of them from abroad.

I sat outside, feeling the evening coming on as the sun fell beneath the ridge. A blackbird stood on the wall nearby, piping sadly in the fading light. I lay back, thinking of England. Soon, it would be time to go home, away from the fat heat and softness of eastern France to a Suffolk where the lean days would cool and shorten, where the exuberant buzz and hubbub of our urban life would be the counterpoint to a whirl of responsibilities. But if I ever needed space in my head, I knew I would think myself back here.

l'Ermitage de Saint-Sorlin is signposted from the D27; and then again from the road between Charcier and Lieffenans up a forest track. It can be reached on foot after about 20 minutes walk. It is always open.