Complex sentence: Millar was vicar of Holy Trinity Brompton from 1985 to 2005 and was the principal person responsible for the Alpha course, succeeded as vicar and the main energy behind the development of Alpha by Revd Nicky Gumbel.
Split into simpler sentences: Millar was vicar of Holy Trinity Brompton from 1985 to 2005 and was the principal person responsible for the Alpha course. He was succeeded as vicar and principal of Alpha by Revd Nicky Gumbel.