Foster was made a deacon on St Peter's Day (29 June) 1980[4] and ordained a priest the following Petertide (28 June 1981) – both times by Kenneth Skelton, Bishop of Lichfield, at Lichfield Cathedral[5] – and began his ordained ministry with a curacy in Tettenhall Regis in Wolverhampton, after which he became chaplain of Wadham College, Oxford.

Following this he was vicar of Christ Church Southgate[6] and finally a canon residentiary and sub-dean at St Albans Cathedral.

On 21 October 2001, he was consecrated a bishop by George Carey, Archbishop of Canterbury, at Southwark Cathedral,[7] to serve the Diocese of St Albans as suffragan Bishop of Hertford.

[10] Foster has spoken out against the Conservative government's changes to the welfare state and austerity measures.

In October 2015, he called proposed cuts to tax credits "morally indefensible": It's clear to me and many others that these proposals blatantly threaten damage to the lives of millions of our fellow citizens.