Oils Ltd, established by Anglo-Persian in 1919 by merging five Scottish oil shale companies (Young's Paraffin Light & Mineral Oil Company, Broxburn Oil Company, Pumpherston Shale Oil Company, Oakbank Oil Company and James Ross & Company Philpstoun Oil Works), was a producer of shale oil. Shale oil production in Scotland ceased in the early 1960s but there was an unsuccessful attempt to revive it in 1973. The company was wound up on 15 December 2010. The Scottish Oil Agency Ltd was a distributing and selling organisation of Scottish Oils Ltd. A Scottish Oil Agency rail tanker is preserved at the Museum of the Scottish Shale Oil Industry. Tanker fleet The British Tanker Company Limited (BTC) was formed in 1915, after the Anglo-Persian Oil Company decided to become a fully self-contained operation, directly owning a fleet of tankers for sea transport. On formation, the BTC had an initial budget of $144,000 with which to build seven steam-powered tankers. The Company's first tanker was the British Emperor, which was launched in 1916. The names of the first seven ships, and all later additions to the fleet, bore the prefix British. Over the next decade, the demand for oil grew throughout the developed world, and the BTC expanded accordingly. By 1924, the fleet numbered 60 ships, with the 60th being the flagship, 10,762 deadweight tonnes (dwt), British Aviator. She was the BTC’s first diesel engine oil tanker, and at that time the most powerful single-screw motor ship in the world. The economic depression of the early 1930s saw rising unemployment amongst merchant navies around the world. However, the BTC undertook a series of strategic mergers, and coupled with the continued support of the Shah of Iran, the APOC succeeded in strengthening its position within the industry. In 1939, the British government chartered the whole fleet of 93 tankers to supply fuel to its armed forces during the Second World War. The fleet lost a total of 42 ships sunk during the war. Within a year of peace in 1945, the BTC fleet had returned to its pre-war total of 93 vessels. The recovery continued with the building of 57 new tankers, each 12,000 dwt, which increased the tonnage of oil transported from Abadan refinery in Iran, whilst remaining light enough for the tankers to pass through the shallow waters of the Suez Canal. In 1946, Princess Elizabeth launched the tanker British Princess for