<Tr> <Td> 2020 </Td> <Td> 29 March </Td> <Td> 25 October </Td> </Tr> <Tr> <Td> 2021 </Td> <Td> 28 March </Td> <Td> 31 October </Td> </Tr> <P> British Summer Time was first established by the Summer Time Act 1916, after a campaign by builder William Willett . His original proposal was to move the clocks forward by 80 minutes, in 20 - minute weekly steps on Sundays in April and by the reverse procedure in September . In 1916, BST began on 21 May and ended on 1 October . Willett never got to see his idea implemented as he died in early 1915 . </P> <P> In the summers of 1941 to 1945, during the Second World War, Britain was two hours ahead of GMT and operating on British Double Summer Time (BDST). To bring this about, the clocks were not put back by an hour at the end of summer in 1940 and, in subsequent years, clocks continued to be advanced by one hour each spring and put back by an hour each autumn until July 1945 . The clocks were brought back in line with GMT at the end of summer in 1945 . In 1947, due to severe fuel shortages, clocks were advanced by one hour on two occasions during the spring, and put back by one hour on two occasions during the autumn, meaning that Britain was back on BDST during that summer . </P>

When did they start changing the clocks in the uk