St Dunstan in the East - St Dunstan's Hill, London, UK - UK Historical Markers on Waymarking.com

The plaque, that has had the Corporation of London crest removed, tells us:

The church of St Dunstan in the East
stood on this site from ancient times.

Sir Christopher Wren rebuilt the church
after the Great Fire of 1666 and the only part
of his design which survives is the tower.

The remainder of the church was rebuilt in 1817
and destroyed by enemy action in 1941.

The garden was created by the Corporation of London
and opened by the Rt. Hon the Lord Mayor Sir Peter Studd
on 21st June 1971.

The City of London website tells us:

The Church of St Dunstan was originally built around 1100 and is a Grade I listed building. A new south aisle was added in 1391 and was repaired in 1631. It was severely damaged in 1666 by the Great Fire of London. Rather than being completely built it was patched up. A steeple and tower was added in 1695-1701 by Sir Christopher Wren.

The Church was again severely damaged in the Blitz of 1941. Wren’s tower and steeple survived the bombing. During the re-organisation of the Anglican Church after World war II it was decided not to rebuild St. Dunstan’s.

In 1967 the City of London decided to turn the remains into a public garden, which opened in 1970.

You really will feel secluded in this gem of a City Garden. Those with green fingers will appreciate the range of plants wending their way around the ruins: the walls and majestic windows have been draped and decorated over time with virginia creeper and ornamental vine, vitis coignetiae, which turns crimson in the autumn. Exotic plants such as the pineapple-scented Moroccan broom, cytisus battandieri, and the new zealand flax, phormium both thrive here in the sheltered conditions. An unusual plant in the lower garden is winter's bark, drimy winteri. Its leaves are high in Vitamin C and were once eaten to prevent scurvy. Near to the fountain is a japanese snowball, viburnum plicatum, whose blossom in late spring is breath-taking.

As mentioned, the church tower is Grade I listed with the entry at the English Heritage website telling us:

Tower, 1698, by Wren. Large, Portland stone structure in gothic style. 3 main stages, Diagonal buttresses rising to octagonal turrets with large finials. Smaller finials between. Stone spire supported on open diagonal arches. Enriched doorways to west and south. North side now obscured by low building. East side rendered where formerly within church. Fine gates and railings to both doorways. Body of church, 1817-18, by David Laing. Destroyed except for walls in World War II. Gothic style with buttresses, traceried windows pinnacles etc. Yellow brick faced externally in Portland stone. North-east vestry. East wall reduced to sill level in centre.