Peter St John began his architectural studies at the Bartlett School of Architecture, University College London, completing them at the Architectural Association in 1984. He worked for Richard Rogers, Florian Beigel, Dixon Jones, and Arup Associates prior to establishing his own practice with Adam Caruso.

Peter taught at the University of North London from 1990-2000. He was a Visiting Professor at the Academy of Architecture in Mendrisio, Switzerland from 1999-2001, and Visiting Professor in the Department of Architecture and Civil Engineering at the University of Bath from 2001-2004. In 2005 he was a visiting critic at the Graduate School of Design at Harvard University. From 2007 to 2009 he was a visiting professor at ETH in Zurich. Peter is a professor of Architecture at London Metropolitan University.