Waterworth practised as a barrister from 1983 until 1987, when he joined the Foreign Office.[6] He was an Assistant Legal Adviser from 1987 to 1990, before being posted to Bonn (which had until recently been the capital of West Germany) where he served until 1994.[6] He then returned to London to work in the Middle East Department, and from 1996 to 2000 was First Secretary at the British Embassy in Rome.[6] After a period in the Northern Ireland Office, Waterworth was Counsellor in Islamabad from 2003 to 2005 and Consul-General in Lagos from 2005 to 2007.[6]