After a consultation with its US counterside, UK space authorities took the initiative to convert its rocket called BLUE STREAK to civilian use. UK authorities asked to France and to other European countries to join the project, that duly enlarged and revised. In a first official meeting of representatives of various European countries, held at Church House, Westminster (London) on January 1961, UK and France presented their proposal. In a second Conference held in Strasbourg almost one month later, the top-level Anglo-French delegation introduced a five-year Initial Programme's proposal. Moreover, they advanced the scheme for a new European launcher organisation. Later, at the Lancaster House conference, held in London from 30th October to 1st November 1961, the delegates of various European countries discussed in details the technical definition of the Initial Programme and they agreed in principle about some programmatic guidelines. This sub-fonds gathers official documents produced by the Lancaster House conference, the real early step which led to the creation of ELDO.