Negotiations on the exact number of aircraft sought by either service were protracted; but it had been established that there was demand for an initial batch of 27 SR.177 aircraft, and that sufficient tooling should be produced to enable the programme to transition rapidly to full-rate production. By April 1956, a consensus had emerged that, in order for the first five SR.177s to be completed by January 1958, these aircraft would be produced without any A.I. radar or the ability to support armaments. In July 1956, funding was secured for 27 aircraft to be produced, the first of which being expected to fly by April (later postponed to October) 1958. On 4 September 1956, a formal contract for the 27 aircraft was issued, which was sub-divided into four batches of five, four, four, and fourteen respectively, although the final eighteen were subject to evaluation and were thus pending confirmation. During 1957, a development contract for the SR.177 was announced for its use with the Royal Navy.