ENGLAND OFFERS no more exquisite experience than King’s College Chapel in winter. Here we can watch a low winter sun pierce medieval windows and send their colours splashing at will across ancient walls. The distance of the refraction sets the colours moving and alive. They are a galliard danced in slow motion. Architecture was never more sublime. And the key is in the glass.

Christmas is when millions of Britons pay their annual visit to their local church. A few go out of piety, but most go out of a residual cultural nostalgia. They go because they did, and thus because they do. They sit in long-neglected pews and hear long-familiar words and hymns. In moments of tedium they gaze at that most neglected art form, stained glass, and wonder what it is about. Such art is neglected, in my view, largely because it has always been associated with churches, and usually with death. A stained-glass window evokes sadness.

Yet in my wanderings round England’s churches it was the glass that most often lifted my spirits. I cannot say that of most glass, installed in the early 20th century and lugubrious with memories of war. Such adornment has flooded so many Anglican churches with gloom. Ask young people what word they most associate with “church” and they reply, “grim”.

And so twice blessed are churches to whom history has bequeathed their ancient glass. Such is the work of the Flemish glaziers at Fairford in Gloucestershire, where the Bible story is told complete in glowing pictures. A similar set survives at St Neot in Cornwall, where it is the more exhilarating for being lost in a jewel-box shrine for passing wayfarers on Bodmin Moor.

Recently restored is the 14th-century Tree of Jesse window at St Mary’s, Shrewsbury, part of a miniature National Gallery of medieval glass in that church. In Long Melford, Suffolk, the east window of Clopton Chapel depicts Christ hanging from a lily in place of a cross, delightfully framed by a glimpse of a hollybush outside. In Ludlow, the Palmers Chapel offers a medieval travelogue, with guild members boasting their exploits on pilgrimage to the Holy Land. The north aisle of All Saints in York displays the horrifying “15 signs of the end of the world” and the celebrated “pricke of conscience” window.

These are among Britain’s most engaging works of medieval art, yet are shockingly unappreciated. They have a purity of colour derived from embedding metal oxides in the glazing process, originally a Byzantine technique. The detail is carried by black pigment, but the effect depends on the arrangement of primary colours, rendered almost Cubist by the supporting lead dividers. The resulting panels, said William Morris, contrive to “capture, store and radiate sunlight”. In Warwick’s 15th-century Beauchamp Chapel the saints’ garments are even studded with glass jewels to dazzle the onlooker. As June Osborne wrote in her book on English stained glass, to picture it is to witness “transparency depicting transparency”.

Not until Morris and his friends began to study the ancients did English glass recapture the magic of the Middle Ages. Any church with Morris glass leaps into life, like the set in Middleton Cheney in Northamptonshire or Gloucestershire’s Selsley, a gallery of works by Rossetti, Webb, Madox Brown and Burne-Jones. After three centuries in which glaziers merely imitated painters, the Pre-Raphaelites rightly saw the manipulation of light as essential to this art. Burne-Jones’s finest work, the huge wheel window at Waltham Abbey, is an explosion of illuminated colour, nature paying homage to the Creation and embodying the cry, “Let there be light”.

Since then churches have been invaded by bad memorial glass. There have been exceptions. Morris was followed by Kempe, Holiday, Clayton and Bell and, more recently, the remarkable team of John Piper and Patrick Reyntiens. Their masterpiece is the Britten window in Aldeburgh, showing scenes from his operas in brilliant reds and greens. My favourite modern work is Laurence Whistler’s decoration of Moreton Church in Dorset, though the glass is etched rather than stained. The effect is to depict the triumph of light over wartime darkness with real Dorset landscape as its backdrop.

The iconoclasts smashed many medieval windows but a newer iconoclast, neglect and decay, smashed many more and left space for mediocrity. I sometimes long for a new iconoclasm to clear bad glass away into store and let the sun spread its own warmth into churches, uninterrupted by pigment. Yet light refracted by nature, be it stained glass or alabaster or fabric or just the leaves of trees, remains a peculiar delight and one that should not be confined to churches. I long for the Victoria and Albert’s superb collection of stained glass — most of it scandalously in store — to be brought out and used to line its underground tunnel from South Kensington station. This would form a sensational procession from transport to art. The French or Dutch would have no inhibitions about such installation.

I regard stained glass as a queen among arts. It has the ostentation of painting, the depth of sculpture and the translucence of film. Philip Larkin called it “sun-comprehending glass”. Through it he could sense “the deep blue air, that shows nothing, and is nowhere, and is endless”. The Middle Ages thought that to endow a stained-glass window was to buy a doorway to Heaven. Who can ask for more?

A new edition of the author’s England’s Thousand Best Churches is published by Penguin in paperback

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