Steen is widely acknowledged as one of the leading figures acting to combat human trafficking in the UK, and in 2015 he was appointed a CBE in recognition of his contribution to the fight against modern slavery.
In February 2016, Steen and Baron Randall of Uxbridge were appointed Special Envoys on modern slavery to the Mayor of London.
[citation needed] Steen worked at the Bernhard Baron Settlement as a youth club leader with Sir Basil Henriques, an East London magistrate, from 1959 to 1967.
Whilst at the Settlement, in 1964, he founded Task Force, an organisation to enable young people to help the elderly, and served as its director from 1964 to 1968, employing 50 full-time staff.
In 1963, Sir John Foster, then MP for Northwich, highlighted Steen's work in an Adjournment Debate in the House of Commons.
As a result, Christopher Chataway MP, a junior minister for education (from 1962 to 1964), offered government funding for Task Force.
The subsequent government, under Prime Minister Harold Wilson, asked Steen to head up a national equivalent to Task Force.
From 1993 to 2012, he was a trustee of Education Extra, a charity set up by Lord Young of Dartington to promote after-school activities in areas of urban deprivation.
Since then there have been two annual events to mark Anti-Slavery Day - on 18 October each year - and to raise awareness of the issue of human trafficking in the UK.
In 2011, activities took place across the country, including a reception at 10 Downing Street to mark the occasion, hosted by Prime Minister David Cameron, whilst the inaugural Human Trafficking Foundation Media Awards, when the Commons Speaker and Home Secretary give awards to journalists, broadcasters and film makers in recognition of their fight to end slavery, took place at Westminster.
In 2006, he established the All-Party Parliamentary Group on Human Trafficking of Women and Children, with the then Speaker of the House of Commons, Michael Martin MP as its first president.
In 2015, Steen served as special envoy to the prime minister and to Parliament's Joint Select Committee on the draft Modern Slavery Bill.
In October 2018, Steen was appointed a specialist adviser, representing NGOs and civil society, on a review into the operation of the Modern Slavery Act.
In November 2018, he was appointed specialist adviser on modern slavery to the Home Affairs Select Committee in the House of Commons.