 Thomson was made a deacon at Petertide 1981 (28 June) and ordained a priest the Petertide following (27 June 1982) – both times by David Lunn, Bishop of Sheffield, at Sheffield Cathedral.He served as assistant curate in the Maltby, South Yorkshire team ministry (1981–1984), and then Team Vicar of St Mary's Church, Banbury (1984–1994), Team Rector of Cockermouth (1994–2002) and finally, before being ordained to the episcopate, the Archdeacon of Carlisle and a canon residentiary of Carlisle Cathedral (2002–2008).Thomson was consecrated as a bishop by Rowan Williams, Archbishop of Canterbury, in Southwark Cathedral on 3 July 2008 and installed as Bishop of Huntingdon in Ely Cathedral on 17 October that year.