Unusually, hardly anything survives from this period, when many changes took place in the décor of the building and in worship here. Much of the colour and carving that adorned the interior was removed by the Reformers in the 1540s and even more by the Puritans in the 1640s.
Major repairs to the tower took place in 1678-9, when the Churchwardens Accounts record payments for 500 bricks, two loads of sand and a ‘load of great stones for the steeple’, also for new lead and the disposal of the old lead.
During the 1700s and early 1800s, like many churches, the building became rather dilapidated. In 1848 John Colman was paid £10.12s. to re-thatch the roof with wheat straw, supplied by local farmer.
A drawing by architect Robert Ladbrooke (see top picture) in the 1820s showed the nave and chancel with rendered walls and thatched roofs, the north porch with its rustic-looking gate and the west window with a jerry-built timber framework replacing its long-lost stone mullions and tracery.
Things continued to deteriorate and the Restoration Appeal leaflet in the late 1860s bemoans ‘the present roof of straw’, supported by ancient timbers which had decayed. The large west window, formerly in the Perpendicular Style, had been ‘replaced by a mean one in no style whatsoever’.
The tower parapet had become unsafe and was ‘temporarily tied together with iron’. Bills were paid in 1863 for repairs to a tower window, also its ‘lattice’ (believed to be the belfry window louvres) and a bell, and £1.4s.4d. for whitewashing the church.
The population of St Mary’s parish had risen from 193 in 1801 to 305 in 1841, so in1846 Forncett was divided into two livings, with the scholarly Revd Dr John Colenso (see bottom picture) appointed as Rector of St Mary’s and to become its most celebrated incumbent. He resided at Tharston Hall until the grand new rectory (now called Forncett Manor) was built for him in 1848. This fine piece of 19th century domestic architecture cost £1,394, of which £1,000 was supplied by Queen Anne’s Bounty, £350 by St John’s College Cambridge and £44 by Colenso himself.