In 1958 the college purchased the site for its fifth and current headquarters in London.
This was on the site of the Someries House on the corner of Regent's Park, Camden. The original building, designed by John Nash, had suffered severe damage from World War II and the building was so bomb damaged that it was approved for destruction, provided that the new building was in harmony with the nearby Regency architecture in 1 to 10 St Andrews Place.
Five architects were interviewed for the chance to design the new headquarters. The controversial pioneer of modern British architecture, Denys Lasdun, was chosen. He spent considerable time observing how the college operated before he began designing the building. Through these observations, Lasdun designed a modernist building with classical elements, suitable for ceremonial, social and study activities. The result, opened in 1964, was a critical success and in 1992 Lasdun was awarded the Royal Institute of British Architects Trustees Medal for this outstanding building.