St Mary's Lighthouse is on the tiny St Mary's (or Bait) Island, just north of Whitley Bay on the coast of North East England. The small rocky tidal island is linked to the mainland by a short concrete causeway which is submerged at high tide. The lighthouse and adjacent keepers' cottages were built in 1898 by the John Miller company of Tynemouth, using 645 blocks of stone and 750,000 bricks. It was built on the site of an 11th-century monastic chapel, whose monks maintained a lantern on the tower to warn passing ships of the danger of the rocks. A first-order 'bi-valve' rotating optic was installed by Barbier & Bénard of Paris, very similar to the one they had provided the previous year for Lundy North Lighthouse; it displayed a group-flashing characteristic, flashing twice every 20 seconds. The lamp was powered by paraffin, and was not electrified until 1977; St Mary's was by then the last Trinity House lighthouse lit by oil.