He was the founder president of the
National Union of Students, being elected their first president in 1922 when the Inter-Varsity Association and the International Students Bureau merged at a joint meeting held at the
University of London. He was the then president of
King's College Union Society. After his experience in the First World War in an address to the
British Association for the Advancement of Science he stated his vision of the role that the NUS would play. The NUS's founding constitution stipulated that it must operate as a non-political and non-religious student organisation as the factional differences among nations were felt to have led to the recent world conflict. The non-political stipulation was dropped in 1969. From its outset the NUS founders were also noteworthy in ensuring that women were involved at its highest levels through a constitutional requirement. Macadam was involved in the formation
Confédération Internationale des Étudiants (International Confederation of Students) bringing together student bodies from the original member countries of the
League of Nations, including the US, and subsequently others. The CIE inaugural conference was held in Prague in 1921. He chaired until 1929 the CIE's commission responsible for
International Relations and Travel. He stepped down as the NUS President in December 1922 to serve as Honorary Organising Secretary, which became in effect their senior executive until 1929. While still at Cambridge, he was able to obtain the financing for a permanent headquarters for the NUS at Endsleigh Street, London, W.C.1.(opened in 1925). Its headquarters remained there until the properties were sold in 2010 to acquire their new building
Macadam House at 275 Gray's Inn Road, London. In 1927 Macadam spearheaded a successful fundraising appeal to endow the Union and place it on a sound financial footing. He was one of the original trustees of the National Union of Students and remained one until the end of his life. The main students' union building and Faculty of Engineering at King's College's Strand campus is named the
Macadam Building in his honour (opened 1975). In 2004, KCLSU President Michael Champion instituted the
Macadam Cup, a day of sporting excellence between medical and non-medical students at the college. A new NUS National Headquarters was named
Macadam House in 2013 at 275 Gray's Inn Road, London, WC1X 8QB. ==Royal Institute of International Affairs (Chatham House)==