18:00Six O'Clock News21/02/2016 Boris Johnson backs leave campaignBBC Radio 4 Duration: 15 minutes Sun 21st Feb 2016, 18:00 on BBC Radio 4 LWAvailable for over a yearListen nowBoris Johnson has announced that he will argue for Britain's exit from the European UnionGenresNewsFormatsBulletinsBrandSix O'Clock News Source: BBC Online