finally ceased on 1 December 1933 and the line closed completely on 31 December 1946. The twentieth century The West Highland Line of the North British Railway (as the WHR had become) settled down to a stable existence in the twentieth century, although continuing to lose money. In 1923 the main line railways of Great Britain were "grouped" following the Railways Act 1921 and the North British Railway was a constituent of the new London and North Eastern Railway. In turn this was schemed into British Railways, Scottish Region, when the railways were taken into state ownership in 1948. In 1924 work started on a huge hydro-electric power scheme which led to the establishment in 1929 of the Lochaber Aluminium Smelter near Fort William. The production of aluminium requires large quantities of electric power, and the decision on location of such a plant is driven by the availability of cheap power. Alcan took over the plant in 1981; the finished metal provided business for the line. In 1931 the Lochaber power scheme was inaugurated; it required a diversion of nearly 1.5 miles of the line alongside Loch Treig; a dam was built across the northern end and the level of the loch was raised by about 35 feet. The diverted railway is from 78m 100yds to 80m 175yds, and includes a new tunnel 150 yards long. The long-standing lack of employment in the West Highlands once again prompted government intervention when in 1963 an Act of Parliament was passed under which a grant of £8 million was made to Wiggins Teape to establish a pulp and paper mill at Corpach. This came on stream in 1966, and was known as Scottish Pulp and Paper Mills. The process requires plentiful timber and fresh water, and although the latter was freely available, in the longer term it proved difficult to obtain economically priced timber locally, and the plant was closed in 1991. In June 1975 Fort William station was relocated, shortening the line a little, in connection with a road scheme. In 1987 radio electronic token block (RETB) was installed on all of the West Highland Railway system, except for the Fort William station area. RETB enabled safe operation of the long single line sections without signalling staff at stations; the control centre was at Banavie. The points at passing loops at stations were spring operated, and were negotiated at slow speed