By the end of the war, over four million new homes were needed in Britain. A vast number had been destroyed during the war, but fewer than 200,000 had been built between 1939 and 1945. In addition to those destroyed by bombs, houses were required for the two million couples who had married during the war. Emergency measures were therefore needed. The Housing (Temporary Accommodation) Act was passed in October 1944, authorising the Government to spend up to £150 million on the provision of temporary pre fabricated houses. Prefabs provided an important immediate solution to the housing shortage at the end of the war, because of the speed and ease at which they could be built. By January 1948, almost 160,000 had been built and allocated at a cost of almost £216 million. Each unit had an average cost of £1300. Although built only as an emergency measure, many prefabs were still being lived in over 40 years after they were first constructed. The Arcon Mark V was the most common prefab type, built from corrugated asbestos and lined with plasterboard. Its low-pitched corrugated iron roof with a rolled ridge was a distinctive feature. Although the vast majority of prefabs were the Arcon Mark V there were other models: Uni-seco: manufactured by the south London based company Universal Selection Engineering Company. 30,000 Uni-seco prefabs were built and were characterized by their flat roof, corner windows and a glass fibre porch. Tarran: a slightly larger prefab made by the family construction company Tarran in Hull. Phoenix: the cheapest prefab which was similar to the Arcon but without the curved roof and with smaller windows. The 'Dig for Victory' campaign brought the arts of vegetable growing and 'allotmenteering' to a fine peak. On 5th September 1939 the Minister of Agriculture, Sir Reginald Dorman Smith, appealed to the nation: 'Half a million more allotments properly worked will provide potatoes and vegetables that will feed another million adults and one and a half million children for eight months out of twelve. Millions of instruction leaflets were issued, and the number of allotments rose from 815,000 in 1939 to 1,400,000 in 1943. Onions, cabbages and runner beans sprang up where they had never been before: in rose gardens, public parks, on top of Anderson shelters. In the moat of the Tower of London, long rows of green vegetables flourished; in Hyde Park within sight of the Albert Memorial the turf was dug up by a spade wielding army of potato growers, and tomato plants were ranged in the window boxes of London clubs. The 'Dig for Victory' movement was a success because it actually encouraged something that millions of British people enjoyed doing anyway. That it was necessary is beyond doubt. War had made the importing of food a hazardous business, and yet the nation depended on imports for its survival. As the U-boats in the Atlantic sank an increasing tonnage of merchandise, it became obvious that self-help on the Home Front was vital. As well as encouraging the amateur grower, the Government also urged farmers to produce more food; in some places, such as the Wiltshire downs, the landscape was dramatically altered as ploughland replaced pastureland for the first time in centuries. Britain's output of home-grown wheat, barley and potatoes was almost doubled, and it became necessary to import only one-third of the nation's food instead of the two thirds of pre-war years.