By the mid 1920s the post-war period of prosperity was well and truly over. The re-introduction of the Gold Standard by Winston Churchill in 1925 kept interest rates high and meant UK exports were expensive. Coal reserves had been depleted during the War and Britain was now importing more coal than it was mining. All this and the lack of investment in the new mass-production techniques in industry led to a period of depression, deflation and decline in the UK’s economy. Poverty amongst the unemployed contrasted strikingly with the affluence of the middle and upper classes. By the mid 1920s unemployment had risen to over 2 million. Particularly affected areas were the north of England and Wales, where unemployment reached 70% in some places. This lead in turn to the Great Strike of 1926 (see picture below) and, following the US Wall Street crash of 1929, the beginning of the Great Depression of the 1930s.