"WHAT," enquires Sir John, after the service, "is 'the Proper'?" I explain, and we all go home little the wiser. It is St Swithun's, and the sun stares down on us. Lunch in the wet-but-warm garden, and kindly joined by the white cat. Yesterday, we travelled 100 miles to Helpston to honour John Clare, our natural-history poet sans peer, and I gave my 31st presidential address in the marquee.

We went to the Blue Bell, the pub where he worked as a youth, doubling the professions of ploughman and potman. Morris dancers clicked and cried in the car park. Schoolchildren had placed "midsummer cushions" round Clare's grave. These are made by sticking wildflower heads into turf. Clare wrote about what I call his "commonwealth of flowers".

The most terrible thing for him during his long asylum years was the deprivation of the seasonal countryside, for, like all village people, his interior clock kept time with that of the birds and plants. He complained to a friend: "Like the caged Starnel of Sterne, I can't get out. . .

"I love the rippling brook and the singing of birds. But I can't get out to see them or hear them - while other people are looking at gay flower gardens. I love to see the quaking bull rushes and the broad lakes in the green meadows, and the sheep tracks over a fallow field, and a land of thistles in flower. . . I am in this damned madhouse and can't get out."

James, the chaplain of Chelmsford Prison, comes to evening prayer with us, fresh from the myriad troubles of men who deservedly yet tragically can't get out. As a nation, we are notorious for locking people up and forgetting them. George Fox could never forget the teenaged James Parnell, who had walked all the way to Carlisle to be converted by him and made a member of the Society of Friends, and who was now thrown into prison in Colchester to be slowly murdered by the gaoler's wife. So Fox visited him.

Jesus said that when we visit someone in prison we visit him. We can visit prisoners by not forgetting that they exist. The demented are now prisoners in the old people's home. How can they be visited? Clare's madness never sounds very mad to me. A multiplicity of difficulties had brought him down. A couple of signatures had confined him for ever. Except that his poems ran free.

Clare's feelings towards flowers were intimate and profound, and not unlike those of a child who runs towards them. He and his friend Tom Porter "used to go out on Sundays to hunt curious wild flowers". And when he was "down", he would write to Mr Henderson, Lord Fitzwilliam's head gardener, to ask him to bring him both cultivated and uncultivated flowers. They grew side by side in Clare's own garden.

For the poet, botany became both part of his humanity and his theology. They had rarity, but not rank. He would write compulsively about them, in and out of his "prison".

Thirty years ago, it was chemical sprays which threatened our wild flowers. Now it is the lawnmower. Stripes are part of our worship. Clare taught his neighbours what to find in the ruts. Such stamped-on treasures!