Ancient Monuments

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Two post mill mounds 560m and 660m north west of St John the Baptist's Church

A Scheduled Monument in Bythorn and Keyston, Cambridgeshire

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Latitude: 52.3707 / 52°22'14"N

Longitude: -0.4763 / 0°28'34"W

OS Eastings: 503831.541

OS Northings: 275830.8216

OS Grid: TL038758

Mapcode National: GBR FZ8.6DY

Mapcode Global: VHFP2.PNKZ

Entry Name: Two post mill mounds 560m and 660m north west of St John the Baptist's Church

Scheduled Date: 30 November 1925

Last Amended: 18 September 2001

Source: Historic England

Source ID: 1020123

English Heritage Legacy ID: 33356

County: Cambridgeshire

Civil Parish: Bythorn and Keyston

Traditional County: Huntingdonshire

Lieutenancy Area (Ceremonial County): Cambridgeshire

Church of England Parish: Keyston St John the Baptist

Church of England Diocese: Ely


The monument includes two post mill mounds in two areas of protection,
situated 560m and 660m north west of St John the Baptist's Church, in a field
and spinney that were formerly part of Middle Glebe Field. While the wooden
superstructures of the post mills no longer survive, the mounds, which
supported their foundations, are preserved as substantial earthworks
surrounded by ditches from which earth was dug in the construction of the
mounds. The mill mounds, which are situated on the northern side of the
ancient Keyston to Titchmarsh trackway, overlie ridge and furrow cultivation
remains and are of medieval or post-medieval origin.

The northernmost mound has a diameter of 22m and stands to a height of 2m from
the bottom of the ditch. On the south western side it extends into a ramp
approximately 3m long, which connected the post mill on the mound with the
adjacent trackway. The centre of the mound is marked by a partly infilled
depression, now up to 0.5m deep, which is thought to indicate the position of
the mill's central post. The encircling ditch is C-shaped and survives as a
shallow depression of 1.5m wide, except on both sides of the ramp, where it
widens into two small ponds, which are water-filled in winter.

The southernmost mound covers an area 20m in diameter with a height of 1.5m
from the bottom of the ditch. The central depression in the top of the mound
is less pronounced than that of its northern neighbour and is approximately
0.3m deep. The encircling ditch survives as a shallow depression up to 3m
wide, except on the south west where mound and ditch have been cut by a modern
boundary ditch, destroying any evidence of a ramp.

All fence posts are excluded from the scheduling, although the ground beneath
them is included.

The site of the monument is shown on the attached map extract.
It includes a 5 metre boundary around the archaeological features,
considered to be essential for the monument's support and preservation.

Source: Historic England

Reasons for Scheduling

Post mills were the form of windmills in the medieval period in which the
wooden superstructure rotated about a central vertical post. The central post
was mounted on cross timbers which were stabilised by being set into a mound.
This mound might be newly built but earlier mounds were also frequently
reused. The whole superstructure of such a mill was rotated to face into the
wind by pushing a horizontal pole projecting from the mill on the opposite
side from the sails. The end of this pole was supported by a wheel and
rotation eventually resulted in a shallow ditch surrounding the mill mound.
Post mills were in use from the 12th century onwards. No medieval examples of
the wooden superstructures survive today but the mounds, typically between 15m
and 25m in diameter, survive as field monuments. In general, only those mounds
which are components of larger sites or which are likely to preserve organic
remains will be considered worthy of protection through scheduling. However,
some mills reused earlier mounds, such as castle mottes and barrows, which are
worthy of protection in their own right.

The two post mill mounds 560m and 660m north west of St John the Baptist's
Church survive in good condition. They will preserve evidence on the structure
of post mills, while deposits preserved in the ditches may shed light on a
range of aspects of the medieval environment, such as climate, flora and
fauna. Their relationship with associated features such as the ancient
trackway to the village and ridge and furrow may contribute to an
understanding of the economy of the settlement.

Source: Historic England

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