This is the first critical and biographical account of Sir Leslie Martin (1908-2000), one of the leading modern architects of post-war Britain and perhaps best known for the Royal Festival Hall (1948-1951) and his controversial Whitehall masterplan (1964-1970). He was also remembered as a key figure in architectural education, having been the first-ever Professor in Architecture at the University of Cambridge and the Chair of the 1958 Conference, which was fundamental in shaping the mode of architectural education thereafter in the UK. The book also uncovers the crucial role of his wife and architectural partner Sadie Speight in these remarkable achievements, which has previously gone unappreciated, as is often the case for most female architects in couple architect partnerships in the 20th century. This book uncovers the crucial role of Sadie Speight in the development of modern design and architecture, within and beyond her professional partnership with Martin. Their personal and professional life is discussed in such a way that it interweaves with the changing political, social and economic circumstances at certain times. Through the selection of unpublished drawings and records, this book provides new insights into various contexts and key people that helped shape and support Martin's career.