 He served as the party's joint leader from 1970 until 1972, then as its sole leader from 1973 to 1984.Under his leadership Alliance participated in successive assemblies that sought to solve the debate on the province's position, including the Northern Ireland Assembly, 1973 in which Napier was a minister in the power-sharing Executive.In 1979 he came closer to winning a seat in the Westminster Parliament than any other Alliance candidate up to that point when he was less than a thousand votes behind Peter Robinson's winning total in Belfast East in a tight three-way marginal.