The screens were once the main visual showpiece of a church

Rood screens? Surely you can’t write a whole book about them – and, if you do, surely it would be unbearably boring? But in fact, Richard Hayman can write a book about them – not least because he is an expert in these matters, having also written Church Bench Ends and Misericords. And, no, rood screens aren’t boring – even if you aren’t an obsessive church-crawler.

The screens – which divide chancel from nave, and were originally topped with a rood, the Anglo-Saxon word for a cross, with the crucified Christ flanked by Mary and John the Evangelist – are crucial to the layout of a church, to English church history and to the aesthetic understanding of our most important buildings, our parish churches. And Hayman, in his gentle, easy-going, unacademic prose, is the perfect rood-screen guide.

What a joy to discover new architectural language: the rood loft, above the screen where singers would gather, is known as a “perke” in Norfolk, and a “candlebeam” in Suffolk. (Candles were set up on rood screens – the rood beam at Westwell, Kent, could accommodate 60 candles, and St Petroc, Exeter, went through 4,200lb of candles in 1541 alone, all burnt on its rood screen.)

The rood screen was a vital part of the church – screening the priest’s sacred rituals from the congregation, although worshippers were allowed a glimpse through the screen’s decorated openings.

At Mass on Sundays, the priest would pass through the door in the screen to read the Epistle and the Gospel. And, at Easter, the day of the year when the laity received Communion, the priest carried the consecrated Host through the screen. During Lent, the rood was veiled; the veil was lifted on Palm Sunday. The Gospel was often then sung from the rood loft for added effect. Rood screens were the number one visual showpiece of the medieval parish church, and represented the biggest investment made by the parish.

And the emphasis was on the parish. While the rector paid for the chancel, the parish paid for the nave and the rood screen. Churchwardens emerged as a result of the need to administer funds and sort out building works. At Bodmin Church in Cornwall, 447 donors in the parish paid for the rood screen. That’s why the screens tend to be decorated on the west, nave-side only – for the benefit of the congregation, not the priest.

And oh, how beautifully they are decorated. First, in their sculptural bones. In south-west England and the Welsh Marches, the cornices are often carved into vine trails. The screen cornice in Partrishow, Powys, is a joy, with its interlocking leaves and tendrils, topped by panels that imitate Gothic tracery.

Then came the painting on top of the carving. Rood screens also worked as image galleries, painted with angels, patron saints and local donors. All life is to be found on rood screens, from St Apollonia – invoked in prayers by toothache sufferers – to the Greek Sibyl at Ipplepen, Devon, a pre-Christian prophetess said to foretell the coming of Christ.

Rood screens weren’t ordered to be removed at the Reformation – although rood lofts were – but they did lose their primary function, of separating the congregation from the priest. Nevertheless, many screens were ripped out and others had their images whitewashed or desecrated, particularly the faces of the saints.

An attempt was made to restore the screens under Queen Mary but, by then, the colour and magnificence of the pre-Reformation Church were largely lost.

Still, plenty of pre-Reformation rood screens survive; the earliest, from the late 13th century, are at Stanton Harcourt, Oxfordshire, and Kirkstead, Lincolnshire. Most surviving screens are from the 15th and 16th centuries. In the remoter corners of the country, they were never touched. Thus the beautiful glut of them in Herefordshire and Monmouthshire – which has the best surviving screen, loft and tympanum in England or Wales, at Bettws Newydd.

Slowly, over the centuries since the Reformation, there has been a gathering interest in rood screens. In the 17th century, several new chancel screens were built, with the royal arms where the medieval rood would have been. Under the Victorians, there was plenty of cleaning and repainting of neglected, medieval screens. The greatest modern revival came under the sainted Sir Ninian Comper (1864-1960). I have made recent pilgrimages to his screens at St Mary the Virgin, Wellingborough, Northamptonshire, and Wimborne St Giles, Dorset. Both screens look like they were made yesterday – but they’re neither kitsch nor pastiche. They bring a rush to the heart; a momentary glimpse of all the gleaming splendour of the pre-Reformation parish church.

Harry Mount is author of A Lust for Windowsills: a Lover’s Guide to British Buildings (Little, Brown)