Having now visited several thousand English churches, it is inevitable that some of them begin to blur into each other. But there are other churches which stick so firmly in the mind that they are easily familiar, and return visits to them are eagerly anticipated. And yet, these are the very churches at which it is always possible to notice something new, and this church is one of them, for not unreasonably St Peter is one of the dozen best and most famous parish churches in England. Alec Clifton-Taylor thought it was the best.

Of course, such claims can made for many big churches; but St Peter is not just special for its size. It is indeed magnificent, but also infinitely subtle, the fruit of circumstance and the ebb and flow of centuries. There is a sense of community and continuity as well; this is no mere museum, and it is not simply St Peter's historic survivals that attract its champions. At 160 feet long it dwarfs other East Anglian giants like Southwold, Blythburgh, Cley and Cawston. Only Salle gives it a run for its money. It is also a welcoming church, as all great churches should be. But even if it were kept locked, which it isn't, there would still be so much to see here that it would be worth the journey.

This part of the county has a character more commonly associated with Cambridgeshire, and of course we are only a couple of miles from the Nene which forms the border between the two counties. Walpole St Peter is closer to Peterborough and Cambridge than it is to Norwich. Indeed, it is closer to Leicester than it is to Great Yarmouth at the other end of Norfolk, a reminder that this is a BIG county. Today, the Norfolk marshland villages tend to be rather mundane, apart from their churches of course. In this curiously remote area around the Wash delineated by Lynn, Wisbech and Boston, there is an agri-industrial shabbiness accentuated by the flat of the land. But you need to imagine the enormous wealth of this area in the late medieval period. The silt washed by the great rivers out of the Fens was superb for growing crops. East Anglia, with the densest population in England, provided a ready market, and the proximity of the great ports gave easy access for exports. And then there was the Midlands and the North which could be accessed by the east coast ports.

The landowners and merchants became seriously wealthy, and according to custom bequeathed enhancements to their parish churches to encourage their fellow parishioners to pray for their souls after they were dead. This was nothing to do with the size of the local population; in England's Catholic days, these buildings were not intended merely for congregational worship. The fixtures and fittings of the parish churches reflected the volume of devotion, not just the volume of people. In areas where there was serious wealth, the entire church might be rebuilt.

But here at Walpole St Peter there was another imperative for rebuilding the church. In the terrible floods of the 1330s, the church here was destroyed, apart from its tower. Before it could be rebuilt in the fashionable Decorated style, the Black Death came along and took away fully half of the local population. However, the economic effects of the pestilence would turn out to be rather good for East Anglia in the long term, and by the early-15th century churches were being rebuilt on a grand scale all over Norfolk, Suffolk and Cambridgeshire. Walpole has two late medieval churches - St Andrew on the other side of the village is very fine, but St Peter is the one that puts it in the shade.

The nave came first, the chancel following a few decades after. Eventually, the tower would also have been rebuilt, in a similar scale to the rest of the church. How amazing it might have been! We only need to look a few miles over the border to Boston to see what could have been possible. But the English Reformation of the 16th century brought an end to the need for bequests, and so the late 13th century tower remains in place to this day.

The vast church sits hemmed in to the north and east by its wide churchyard. The battlemented nave and chancel are a magnificent sight, most commonly first seen from the village street to the north. Rendering accentuates the reddishness of the stone, and the finest moment is probably the conjunction between nave and chancel; spired roodstair turrets rise to the gable, and at the apex is a glorious sanctus bell turret. The stairway on the north side is supported by a small figure who has been variously interpreted as the Greek god Atlas, the Fenland giant Hickathrift, or as anyone else I suppose.

The chancel is beautiful, but its most striking feature is the tunnel that goes beneath its eastern end. One of the features of the late medieval English Catholic church was liturgical processions, but when this chancel was extended in the 15th century it took the building right up to the boundary of consecrated ground. To enable processions still to circumnavigate this building, the tunnel was placed beneath the high altar. Such passageways are more common under towers, and there are several examples of this in Norfolk, but that option was obviously not possible here.

There are lots of interesting bosses in the vaulting. It isn't just the medieval past that has left its mark here. The floor of the tunnel is flagged, and there are horse-rings in the wall from the 18th and 19th century when it served the more mundane purpose of stabling during services.

Views of the south side of the church are hindered by a vast and beautiful copper beech, but there is no hiding the vastness of the south porch, one of the biggest and finest in Norfolk. The parvise window is as big as nave windows elsewhere; the keys of St Peter decorate the footstool of one of the niches.

And here are some of the finest medieval bosses in Norfolk. The two main ones are the Assumption of the Blessed Virgin, and the Last Judgement. There are characterful animals in the other bosses. Figures in niches include a Pieta, a Madonna and child, and a pilgrim with a staff, pack, and shell on his hat. Also in the porch is a sign reminding you to remove your patens, the hardy wooden clogs common to 19th century farm workers.

So much to see, then, even before you come to push open the original medieval door! And then you do, and the birdsong and leaf-thresh of the summer morning outside falls away, and you enter the cool of a serious stone space. The first impression is of height, because the vista to the east is cut off by an elegant 17th century screen, as at nearby Terrington St Clement. The unifying of nave and tower, almost a century apart, is accomplished by sprung buttresses high up on the west wall, each carved with a figure. Here are the Elizabethan communion table, a hudd ( the sentry box-like device intended to keep 18th century Rectors dry at the graveside) and the perpendicular light through the west windows.

And then you step through the pedimented entrance through the screen into the body of the church, and the building begins to unfold before you. Your journey through it begins.

Some huge churches impose themselves on you. St Peter doesn't. It isn't Salle or Long Melford. But neither is it jaunty and immediately accessible like Terrington St Clement or Southwold, nor full of light and air like Blythburgh. St Peter is a complex space, the sum of its parts, like Cley, and yet more than them, with a sense of being an act of worship in itself.

One of the delights of Walpole St Peter is that many of the furnishings reveal the hands of local craftsmen; the roodscreen dado Saints, for example. There are twelve of them, their naive character reminiscent of Westhall. The six outer saints are women, the inner ones apostles. The two sets are clearly by different hands, and the late Tom Muckley wondered if they were, in fact, from two different screens.

On the north side are St Catherine, the rare subject of the Blessed Virgin and Christchild, St Margaret (the processional cross with which she dispatches the dragon is unfinished), St John, St James and St Thomas. On the south side are St Peter, St Paul, St Andrew, St Mary of Magdala, St Dorothy and St Barbara. I was delighted to be asked recently for the use of my photographs for the information board which explains it.

The nave has a feel that is at once ancient and vital, not so much of age as of timelessness, of continuity. It's the sheer mixture of woodwork that impresses - silvery oak broods in the white light from the high windows. The best of the medieval work is in the south aisle, where the benches are tiered and face inwards. A massive dark wood pulpit and tester broods over the north side. Above all this rises the pale cream of the arcades, topped by the gold of the hanging candelabras, and the towering, serious early 17th century font cover. The font is clearly one of the Seven Sacraments series; but, as at the great churches of Blythburgh and Southwold in Suffolk, the panels have been completely erased. A dedicatory inscription is dated 1537.

As well as wood, metal. The candelabras provide a focus, but there is also one of the latten medieval lecterns familiar from elsewhere in Norfolk, the little lions perky at its feet. The south aisle chapel has a lovely parclose screen with a spiked iron gate. In the north aisle, the chapel has been neatly furnished for smaller scale worship.

And then you step through into the chancel, and this is something else again. Here is true grandeur. This immense spaces rises fully twenty-one steps from nave floor to high altar. Here is the late medieval imagination writ large, compromised in the years since, but largely restored by the late Victorians. You step from subtlety to richness. Niches and arcading flank the walls leading the eye east, their blankness becoming sedilia. In the high niches where once were images, 17th and 18th century worthies have their memorials. Everything leads the eye to the great east window, where excellent 19th century glass completes your journey through the Queen of the Marshlands.

Simon Jenkins, in the often-maligned England's Thousand Best Churches, tends to cast a cold and even sardonic eye on most buildings as he passes by, but at Walpole St Peter even his breath was taken away: it is a place not of curiosity but of subtle proportion, of the play of light on stone and wood. If English churches were Dutch Old Masters, this would be St Pieter de Hooch.

Simon Knott, April 2017

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