Whilst battles were fought across the globe, in Britain, the anti aircraft gun sites acted as the British frontline. From 1941, they were also the first operational war zone women were allowed to work on. To commemorate the 80th anniversary of the National Service Act, James Rogers is joined by Tessa Dunlop, author of 'Army Girls', an intimate look at the lives of the final few women who served in World War Two, and the first women called up to serve both king and country.