During the 1950s and 60s, Forncett continued to function as a single parish, but there was increasing concern that areas such as Norfolk were overserved with expensive-to-maintain churches.
St Mary’s was a candidate for retirement, and after much deliberation the Parochial Church Council set the wheels in motion for its official closure on 30th December 1979.
By 1980 the church was beginning to deteriorate. Many tiles had slipped or fallen, the porch was roofless, cracks between the nave and north tower wall and between the vestry and nave needed repointing. The organ case and vestry panelling needed woodworm treatment, two windows were smashed, and the window stonework together with the tower parapet needed repair.
In June 1982, a Faculty was issued for the disposal of certain contents with the altar, organ and choir stalls remaining for the time being. The three bells were taken down from the tower and given new homes. One, badly cracked, was recast by Taylor of Loughborough and installed in Forncett St Peter’s tower, in memory of Miss Mary Armstrong, a former Headmistress of Forncett School who, at the age of 72, had been tragically murdered.
The Declaration of Redundancy came into effect on 1st March 1985. Four years later the font was taken to the cloister garden at the Roman Catholic Shrine of Our Lady of Walsingham at Houghton St Giles.
The building and its churchyard continued to deteriorate and various ideas for new uses were explored. It was commercially advertised for alternative use in 1996; a London-based trust investigated the church being converted to holiday accommodation, and commissioned a report by architect practice Feilden & Mawson in the hope of conversion into two holiday homes – but nothing transpired.
Further decay continued over the following decade.