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The Shorts design became the "SA.4", later known as the "Sperrin". It was, as intended, a conservative design, basically a jet-powered version of a World War II style bomber with conventional tail assembly and straight wings (though the wings did have leading-edge sweep). The only particularly unusual feature was that the four Rolls-Royce Avon engines were fitted in nacelles mounted in the midwing, with two engines in each nacelle mounted in a top-and-bottom fashion.

The first prototype performed its initial flight on 10 August 1951, with Shorts chief test pilot Tom Brooke-Smith at the controls. It was fitted with Avon RA.2 turbojets with 26.6 kN (2,720 kgp / 6,000 lbf) thrust each. In March 1950, well before the initial flight, the Air Ministry had decided that the Sperrin wouldn't be put into production, but work on the two prototypes was allowed to continue.

The second prototype performed its first flight on 12 August 1952. It was fitted with Avon RA.3 turbojets with 28.1 kN (2,950 kgp / 6,500 lbf) thrust each. The two Sperrin prototypes were used in a variety of trials through the 1950s, including engine tests for the big de Havilland Gyron turbojet, with 66.7 kN (6,800 kgp / 15,000 lbf) thrust, with the nacelles modified to accommodate a Gyron in the lower half and an Avon in the upper half; the "Blue Danube" atomic bomb; and the "Blue Boar" TV-guided missile, which did not see service. Both Sperrin prototypes were scrapped in the late 1950s.