After his election to Parliament Best was driving when his car was involved in an accident resulting in the death of his personal assistant

He was cleared of responsibility

During the privatisation of British Telecom, individuals were limited to a single allocation of shares. Best submitted several applications by using minor variations of his name.

On 30 September 1987, he was sentenced to four months' imprisonment for this deception and was fined £3,000. On 5 October 1987, the Court of Appeal ruled that his jail sentence was too harsh, and Best was released but his fine was increased to £4,500.

Despite Best’s conviction for fraud, in 1987 he became the Chairman of the Executive Committee of the World Federalist Movement, but he transitioned to the Secretary role in 2018. He is the former Chair of Parliamentarians Global Action. He was Director of Prisoners Abroad 1989–93. He was Chief Executive of the Immigration Advisory Service 1993–2009. He was Chairman of the Council of the Electoral Reform Society 1998–2003 and served on its Council for fifteen years. He was Chairman of Electoral Reform International Services Ltd 2004–14. He is Chairman of Conservative Action for Electoral Reform. In 2003, he was named by The Guardian as one of the 100 most influential people in public services in the UK.

In April 2010 he took up the post of Chief Executive of Freedom from Torture (formerly Medical Foundation for the Care of Victims of Torture), where he remained until 2014. He was then appointed the first Chief Executive of SurvivorsUK which he left in April 2017 in order to undertake consultancy and more charity work. He is currently Chair of the Universal Peace Federation (UK), Chair of the Wyndham Place Charlemagne Trust charity and of Charity 2020 as well as Secretary of both the European Movement and the Parliamentary Outreach Trust. In October he was appointed to the Board of ARHAG Housing Association and as Secretary of the PCC of St James's Church, Piccadilly, London.