Castle Down

There is a long history of human habitation with 66 cairns (usually burial sites) dating to the Bronze Age.[1] In addition, within 100 m (328 ft) of the southern boundary of the SSSI, there is an Iron Age field system, associated hut circles and large middens covering 3 ha (7.4 acres). The huts are 5 m (16 ft) to 20 m (66 ft) apart and have diameters ranging from 5 m (16 ft) to 7 m (23 ft) while the middens are up to 11 m (36 ft) long, 10 m (33 ft) wide and 1 m (3.3 ft) high. (grid reference SV 888156) The field system was reused in the 19th century.[2]

The artillery fort on the highest point of the west side of Chapel Down, and now known as King Charles's Castle (grid reference SV882161), was built between 1548 and 1554 in the reign of King Edward VI (1537–53). It was built to guard the northern, deep water approach, to New Grimsby harbour, although it proved to be badly sited to fire on ships below, or to withstand attack from the landward side. For a short time it was the main stronghold in the islands but was replaced by Star Castle on the Garrison, St Mary’s in the 1590s. It was later used as a quarry for the building of the nearby fort known as Cromwell’s Castle. The name, King Charle's, comes from the occupation by Royalist forces – the Parliamentarians took Tresco in 1651 by landing on the other side of the island.[3] In March, 1651 a Dutch fleet arrived off the islands demanding reparations from Royalist privateers. The Dutch threat was countered by Admiral Robert Blake who captured the islands from the Royalists in June. The round tower of Cromwell's Castle (grid reference SV881159), built on the site of a previous blockhouse, was completed the following year to guard the deep water approach to New Grimsby harbour. It was updated around 1740 with a platform built for cannon on the seaward side.[4]

In 1652 the Parliamentary Survey of Scilly reported a row of shallow pits and spoil heaps (grid reference SV884164) following, in part the line of a tin lode. The pits were mostly 1.8 m (6 ft) to 2.4 m (8 ft) deep with some shafts to 7.3 m (24 ft). At the western end was an adit. The mining started in the 1640s and ended by 1652 and was said to be of no value.[5]

Piper’s Hole is a deep cavern reached by scrambling down the north coast cliff. The cave consists of a 20 m (66 ft) long boulder–filled passage leading to an underground pool. With the arrival of tourism in the 19th century a punt was kept there and was used to take tourists to the inner chamber.[6]

Castle Down is the name given to the northern part of the island of Tresco and is a 35 m (115 ft) plateau of coarse–grained Hercynian granite. The southern edge of the Late Devensian ice sheet probably reached the northern islands of the Isles of Scilly about 18,000 years BP (before present) and there are glacial outwash gravels on the northern part of the downs with erratic pebbles.[6] Raised beach deposits are exposed on the cliffs between Cromwell’s Castle and Grimble Porth. The thin skeletal podzolic soils and extreme exposure to salt laden winds have led to the development of a wind–pruned, lichen–rich, “waved” maritime heath dominated by heather (Calluna vulgaris).

The northern part of Tresco is designated as the Castle Down (Tresco) Site of Special Scientific Interest for its waved maritime heath, its lichen flora, a breeding colony of Common Tern (Sterna hirundo) and for its geology. The SSSI was first notified in 1971, re–notified in 1986 and covers most of the higher land and cliffs to the north of the inhabited area of the island.[7]

• Isles of Scilly Wildlife Trust

• The Isles of Scilly Wildlife Trust
• The Isles of Scilly Area of Outstanding Beauty
• Isles of Scilly Seabird Recovery Project
• Lowland heathland - a cultural and endangered landscape
• The Megalithic Portal