Because of the proliferation of rocks and islets the waters around the Isles of Scilly have always been hazardous to shipping, especially in the days of sailing ships when vessels were at the mercy of the winds. Waters were less well charted and navigational aids were limited in their effectiveness.
The first lighthouse on the Islands was built on St Agnes in 1680. It was coal fired until 1790 when it was converted to oil. It stands 23 metres tall and is located at the highest point of the Island, some 500 metres or so inland. It was eventually decommissioned in 1911 when the Peninnis lighthouse was built on St Mary’s. The St Agnes now stands as a quite prominent daymark.
The daymark on St Martin’s is a distinctive feature of the landscape and is very conspicuous with its red and white bands. It was erected in 1683 and is the earliest surviving dated beacon in the British Isles. It is 11 metres tall and stands at the edge of Chapel Down, overlooking the north east coast of the Island.
By far the most important lighthouse is Bishop Rock. Its importance to shipping approaching from the south west and, indeed, to those passing by on other busy routes, cannot be overestimated. It was built with great difficulty in the treacherous seas in 1858 and reaches a height of 44 metres above the mean high water mark. It is the second tallest lighthouse in Britain. It was capped with a helipad in 1976 and became fully automated in 1992. Its light flashes every 15 seconds and has a range of 20 nautical miles (37 km).