[1] Humphreys worked as a civil servant, negotiating environmental legislation with the European Union and later becoming Head of Corporate Communications at the Prime Minister's Office.
He works for the public policy consultancy Woodnewton,[2] and was formerly a trustee of the Woodland Trust.
[3] Humphreys is the author[4] of Negotiating in the European Union: How to Make the Brussels Machine Work for You[5] and collaborated with Caroline Lucas on two books, Honourable Friends?
Quite separately, Humphreys has pursued a career as writer of popular fiction.
Starting with Sleeping Partner in 2000,[6] he received praise from Colin Dexter, who stated that the book was: "[a] splendid debut in crime fiction - more please, Mr Humphreys".