Using the H.P.80 design as it stood in early 1948, a 40% scale model was commissioned.
Due to lack of design capacity, the aircraft was sub-contracted to General Aircraft, which were shortly after taken over by Blackburn Aircraft. Blackburn allocated the Y.B.2 designation to the project. Initially the aircraft was to be a modified Supermarine Attacker, but was eventually changed to become an Attacker/Swift hybrid, also receiving the Supermarine 521 designation.
A single H.P.88 was produced, but by the time construction started the H.P.80 design had changed significantly - effectively marking worthless the aerodynamic test results, and by the time the H.P.88 first flew construction of the prototype H.P.80's was already well advanced.
The aircraft was found to be very unstable, and the aircraft crashed after only two months, and construction continued on the H.P.80 without any further large scale testing.