Haydn was born in Newport, South Wales. His father was an evangelist and the on-shore link at Newport docks for the Merchant Navy Christian Fellowship.
The family lived on a white working class council estate. He says, "The only ethnic minorities were those who called at and were made welcome at our home as they looked for Christian fellowship when their ships docked at Newport. This gave me from an early age a window on the nations of the world and we loved every moment of it".
Haydn worked as a gardener/groundsman from 1968 to 1987 when he went to Baptist College. In 1978 he got involved with praying for Albania and in 1979 made the first of many trips to that country.
After Baptist College, in 1991, Haydn was called to a four-church pastorate in mid-Wales and is still serving those churches. It was those churches that nominated him for the Presidency of the Baptist Union of Wales. During that Presidency he served on General Committee of BMS and from that committee was nominated to serve on BMS Candidate Board.