To meet with the stated requirements, Shorts proceeded to develop their original proposal for the Britannic, which was basically stretched into the Britannic III A. As the design of the proposed aircraft was repeatedly revised, it was progressively becoming less and less common to the earlier Britannia, incorporating a greater proportion of all-new components, sections, and systems instead. Amongst the changes made were a new centre section to the wing which added around to the span and the adoption of the Rolls-Royce Tyne engine. In January 1959, the Ministry announced its selection of Short's design to meet the requirement. Accordingly, in February 1959, work on the Short's project formally commenced, known by the internal designation SC.5/10. On 21 December 1960, a contract for a total of 10 freighters, designated Belfast C.1, was signed.
