One of London’s most remarkable new buildings sits in a nondescript trading estate in Dagenham East. The UCL PEARL – Person Environment Activity Research Laboratory – is a unique purpose-built facility for testing full-size environments to find out how people use infrastructure and cities. Peter Murray visits the building and talks to Penoyre & Prasad architect Michael Fostiropoulos and his client, Professor Nick Tyler, who asked for a building that “would house the world”.