St John the Evangelist's Church, Corby Glen

The Church of St John the Evangelist is the Grade I listed Church of England parish church of Corby Glen, a village in the Lincolnshire Vales of South Kesteven, nine miles south-east of Grantham. It is celebrated above all for its fourteenth- and fifteenth-century medieval wall paintings — among the most extensive in any English parish church, hidden under whitewash for centuries until a churchwarden's discovery in 1939 — including a painting of St Michael and the Virgin of Mercy that is unique in the United Kingdom.

Neither church nor priest was recorded at Corby in the Domesday Book of 1086, and the present building dates from the twelfth century. The fourteenth century added the side aisles — including a Lady Chapel in the north aisle before 1319 — a porch, a short tower and an enlarged chancel, and the earliest wall paintings in the north aisle belong to this period. The fifteenth century brought a massive rebuild: the nave roof was raised and a clerestory added for light, the chancel extended with two new windows, a further chapel created, the tower heightened, and the porch replaced with a priest's room built above it — and more wall paintings joined the earlier ones. The church was restored with new pews in 1860, and the tower restored in 1928 at a cost of £800. The parish register dates from 1561, and the earliest recorded rector is John Obyne in 1551. Victorian incumbents left their mark: the Reverend Charles Farebrother of Trinity College, Oxford — former domestic chaplain to the 1st Duke of Cambridge — held the living from 1851 until his death in 1899, with a residence and eighty-two acres of glebe, and placed a stained glass window in the chancel to the memory of his deceased children; the Reverend Arthur Abbott of Queen's College, Oxford, followed from 1900 into the 1930s. The Grade I listing came in 1968.

The church is of ashlar-faced limestone and rubble, mixing Norman, Decorated and Perpendicular styles, with nave, chancel, north and south aisles, square embattled tower, two-storeyed south porch and chapel. The three-stage tower has a fifteenth-century belfry stage with louvred openings drained by gargoyles, and at the base of its west buttress an inscription names the mason, Thomas de Somersby. The late thirteenth-century north aisle has traceried three-light windows, two added in the fifteenth-century extension; the south aisle is Decorated with Late Perpendicular windows; and the gabled Perpendicular porch, with stone benches within and pinnacled parapet above, carries its priest's room over a pointed-arch entrance. Twenty yards south-west, the churchyard's early nineteenth-century wrought-iron gates and ashlar pillars are separately Grade II listed.

Inside, with seating for 206, the late fourteenth-century nave roof is braced by corbels of grotesque style, and the four-bay arcades stand on piers faceted with four columns under octagonal capitals and Decorated arches — which Pevsner suggests belong to an earlier build, as may the "most oddly" placed plain Norman imposts in the thirteenth-century chancel arch, a view Cox supported. Above the arch the earlier chancel roof line shows, and a small doorway above the pulpit — itself carved with a figure of John the Evangelist — once led to the rood loft. The fittings span the centuries: a thirteenth-century octagonal font on an 1893 marble shaft; a fifteenth-century iron-bound chest by the south door; a seventeenth-century communion rail installed, with splendid practicality, to keep dogs out of the sanctuary; nineteenth-century panelled box pews in the aisles; a chalice of 1609 among the plate; ledger slabs in the chancel; a monument of 1764 to Frances Wilcox in the chancel chapel; and wall plaques by Hawley of Colsterworth in the north aisle. Stained glass includes two shields and a figure of St John of the fifteenth century in a north aisle quatrefoil, with medieval fragments in other windows.

But the wall paintings are the glory. Pevsner called them "very extensive", singling out the "gigantic St Christopher, originally nearly 11ft high, c.1350" as "a delightful figure". The clerestory carries Nativity scenes — the Virgin, Child and Magi, a shepherd and King Herod. The north aisle shows St Anne teaching the Virgin, and an extraordinary moral composition of the Seven Deadly Sins and a "Warning to Swearers", centred on a Pietà surrounded, in Pevsner's words, by "devils and elegantly dressed youths". The south aisle wall bears a Tree of Jesse within an ogee pattern. And the north aisle preserves that unique fifteenth-century survival: St Michael weighing a soul while the Virgin of Mercy intercedes on its behalf — found nowhere else in Britain.

The tower holds a peal of six bells for change ringing: four cast for the church between 1580 and 1628, joined in 2013 by two bells of 1935 obtained from St Albans, at which point a bell added in 1988 — formerly of St Thomas's church at nearby Bassingthorpe — was removed for sale. The original timber bellframe gave way to steel in 1975, when the bell of the former grammar school, cast in 1691 at the Stamford foundry of Tobias Norris, was hung as a separate Sanctus bell. The organ is a small single-manual instrument of five stops, probably by Taylor of Leicester, obtained from Stamford School in 1949 to replace an 1890 predecessor, and overhauled in 1997 by Aistrup & Hind.

St John's heads the Corby Glen Group of Parishes in the Deanery of Beltisloe and the Diocese of Lincoln, alongside St Andrew's at Irnham, St Nicholas' at Swayfield, St Thomas à Becket at Bassingthorpe, St Mary Magdalene at Bitchfield and St Thomas of Canterbury at Burton Coggles — a quiet Lincolnshire church whose whitewash, once peeled away, revealed one of the great painted interiors of medieval England.