bath, which enabled it to turn much more freely. Two years later incandescent oil burners replaced the old multi-wick burners; they were upgraded with the installation of 'Hood' incandescent burners in 1922. These remained in service until 1945, when they were replaced with electric lamps (powered by Stuart Turner diesel engined generating sets). A separate small Petter-engined generator provided electricity for the keepers' domestic use from 1955; it replaced a petrol-driven machine which had been installed during the war to power a radiotelephone (enabling direct verbal communication with ships, the shore and other nearby lighthouses). The electric installation was upgraded (with the provision of Lister diesel generator sets) in 1973. Difficulty reaching the lighthouse by boat led Trinity House to build a helipad on top of the lighthouse in 1976. That same year a supertyfon fog horn was installed with sounders arranged around the gallery. On 15 December 1992 the tower became fully automated; the lower half of the biform optic remained in use following automation, but the top half was removed and put on display (it is currently in the National Maritime Museum Cornwall). An electric fog signal replaced the supertyfon at this time, sounding a long followed by a short tone every 90seconds; its use was discontinued in 2007. On the 144th anniversary of the destruction of James Walker's original iron tower (), a storm caused severe damage to the gunmetal entry doors, which had to be replaced; they too became an exhibit at the National Maritime Museum in Falmouth. Structure Bishop Lighthouse is often referred to as "King of the lighthouses" and it is indeed a very impressive structure. With a height of the lighthouse is the equal tallest in England, together with Eddystone Lighthouse. Expenditure on the lighthouses at Bishop Rock, include: The first iron lighthouse: £12,500 The second granite lighthouse: £34,559 (equivalent to £ in ) The third improved lighthouse: £64,889 (equivalent to £ in ) Total cost: £111,948 The interior of the light house consists of the following (as described in 1911): Below and inside the lighthouse are 10floors with spiral staircase to the 2nd floor with a door (made from gun metal (likely bronze) and installed in 1887) that leads down an external metal (likely bronze) ladder to climb down to the large exterior base. From the base another metal ladder provides access to a stone staircase to the waterline. Prior to automation,