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Coast Artillery – Searchlight Types

In a memo dated 7 December 1941 from the Commander-in-Chief, Home Forces, he defines the two roles that coast artillery searchlights (C.A.S.L.) fulfil. Each role was provided with a different type of light. These are:

  1. Detection of hostile vessels
  2. Engagement of hostile vessels

Observation lights

This type of light was provided to detect hostile vessels. They could have had either a fixed or movable beam of light but were intended to detect and give early warning to the defences of approaching enemy vessels. They were not intended to concentrate on a single or group of vessels, but once a target was identified they would break off and continue searching.

This observation light sits at Lavernock Point, upriver on the Severn but close enough to Lavernock Battery that vessels could be identified and passed over to the fighting lights attached to each gun.

Fighting lights

This type of searchlight also had a moveable beam and each was allocated to a close-defence gun. It was this light that would have illuminated a target vessel until it had been destroyed or the target had been passed over to another gun and searchlight.

These two fighting light positions are associated with the quick-firing 6-pounder guns of Houton Battery, Orkney. Each gun position had a searchlight and they would work together to engage and destroy fast-moving enemy vessels.

Archaeologically I don’t believe there is any difference between observation and fighting light emplacements. However, their context and position in proximity to a coast battery will dictate their role. Fighting lights will be close to the guns they are supporting, and observation lights will be sited nearer the likely direction enemy vessels may approach from. The role of observation lights is to scan the water and be the first to identify enemy vessels before handing them over to a battery for engagement.

Illuminated area lights

This was the term given to fixed-beam lights to aid the engagement of target vessels by anti-motor-torpedo boat (A/M.T.B.) batteries.

An illuminated area searchlight at Balfour Battery, Orkney. The vertical apertures would have created fixed beams of light to a set bearing and range, and in conjunction with other searchlights, the battery observation post would have a designated area in which to engage enemy vessels.

The original and once secret document can be found in the National Archives contained in record WO 199/524.