Complex sentence: The test programme involved the progressive testing and development of the M.52 by the RAE, initially without reheat installed, with the aim of achieving Mach 1.07 by the end of 1946.
Split into simpler sentences: The test programme would have involved the progressive testing and development of the M.52 by the RAE, initially without reheat installed. The ultimate aim of the tests would have been to have achieved Mach 1.07 by the end of 1946.