In 1987 he was placed at the Harvard School of Public Health, Boston and was also involved in the Tropical Diseases Research Programme of WHO in that year.
In 1997 the Department of Infectious and Tropical Diseases was formed at the LSHTM, which he headed until 2002.
Peter has also been involved in recent years in research on the link between bovine spongiform encephalopathy (BSE) and Creutzfeldt–Jakob disease in humans.
From 1996 to 2004 he served on the Spongiform Encephalopathy Advisory Committee, which advises the UK government on BSE and related issues.
He also serves on a number of international committees relating to intervention studies against some of the major tropical diseases.