A prominent supporter of the United Kingdom remaining in the European Union during the Brexit referendum and of Jeremy Hunt in the 2019 Conservative Party leadership election, he left his post as a Foreign Office Minister when Boris Johnson's premiership began.

He was secretary and national political officer of the Oxford University Conservative Association from 1985 to 1986, JCR president of St Edmund Hall in 1986, and he was also news editor of student newspaper Cherwell while it was under the editorships of Christina Lamb and Anne McElvoy.

[6] He was elected as a Conservative councillor for Abingdon ward on Kensington and Chelsea London Borough Council in 1994, standing down in 2002 after entering the House of Commons.

After leaving Parliament following the 2019 general election, Field was appointed as non-executive chairman of CIB Limited, a subsidiary of the Isle of Man-based investment bank Capital International Group in January 2020.

[8][9] In December 1999 Field was selected to contest the safe Conservative seat of the Cities of London and Westminster following the retirement of former Northern Ireland Secretary Peter Brooke at the 2001 general election.

Field made his maiden speech in the House of Commons on 27 June 2001, when he declared his great political hero to be former Prime Minister Bonar Law.

As a backbencher, Field introduced several high-profile debates on issues of local and national importance such as homelessness, Northern Ireland, Government debt, Heathrow airport, policing in London, social housing, home education and population estimates.

He has run local campaigns on business rates, St Bartholomew's Hospital, assisting the creative industries, the control of rickshaws in the West End, social housing rent rises, the independence of the City of London Police (including its fraud detection expertise) and, in July 2011, successfully argued in Parliament for the Department of Culture, Media and Sport's continuing control of the Royal Parks.

"[11] In 2012, it was reported that the Independent Parliamentary Standards Authority (Ipsa) had plans to reform MPs' pay, which could lead to them facing salary cuts for taking on second jobs.

He expressed concern that their "tent city" was turning into a "semi-permanent encampment" which was disrupting St Paul's Cathedral, a "key iconic tourist site" and place of worship.

He suggested that police should clear the camp at night[19] and later said: "While no one expects anti-capitalism to be a 24-hour activity, I would have hoped the protesters would show a little more respect for the sanctity of St Paul's.

"[20] On 28 February 2012, after 137 days of occupation, Field's initial recommendation became reality following a Court order when the site was cleared by the City of London Police in just 137 minutes.

Field asserted that the Coalition Government's pledge to get "annual net migration down to the tens of thousands" was undeliverable, risked potential harm to the economy and could ultimately be electorally damaging to the Conservative Party.

In 2016, he met Halbe Zijlstra, Leader of the Dutch People's Party for Freedom and Democracy in the House of Representatives, who had made a series of controversial comments about immigrants and political correctness.

[34] A Cabinet Office investigation into the assault allegation, published in December 2019, concluded that he had breached the ministerial code but that he would not receive any sanction as Field was no longer in Parliament.