During World War Two, he formed the Europe Study Group to look at the problems of Europe and the prospects for a non-nationalist Germany, according to Stephen Dorril:
- At the core of the group were a number of emigré Germans destined to play a role in the European Movement, such as the future leader writer on the Observer, Richard 'Rix' Lowenthal. Interviewed for recruitment by MI6, Astor was turned down for a full-time post but was subsequently used by MI6 officer Lionel Loewe to establish contact with the German opposition. Employed as the press officer in Lord Mountbatten's Combined Operations Headquarters in London, Astor continued with his group, which drew on the ideas of the Cecil Rhodes-inspired Round Table Group and its belief that 'the British Empire should federate'.
- John Mulholland, Did former Observer editor David Astor save Nelson Mandela's life?, The Observer, 3 December 2011.
- David Astor, Telegraph, 8 December 2001.
- MI6: Inside the Covert World of Her Majesty's Secret Intelligence Service, by Stephen Dorril, Touchstone, 2002, p.456.