Why was unemployment high during Margaret Thatcher's reign?

When Thatcher came to power, the UK's budget was in such a mess that the IMF had been called in by the previous government to stop us going bankrupt. A total over-haul of the economy was required, scaling back public spending and ending government support of failing businesses (such as mining). This led to a lot of public sector jobs being cut to try and save money, and obviously there were a lot of people losing their jobs as the private sector tried to get back on its feet. The high unemployment at the start of her time as Prime minister was due to a mixture of economic factors, and the policies put in place to try and fix the economy. By the end of her time in charge, however, unemployment had fallen drastically.