25 Sqn's history states:
In 1933 the Squadron had achieved such a high standard of proficiency that it won outright the prestigious Phillip Sassoon Fighting Area Trophy with a score of 99.9%.
First awarded in 1927 "to be competed for by the fighter squadrons of Air Defences", the trophy seems to have iterated over the years from its original purpose and has been awarded, as mentioned in posts above, to cover other worthwhile skills and proficiencies that include excellence in Bombing, Navigation and Apprentice skills among others.
Which makes me wonder whether there is but one trophy or many.
PS Digging around and a further Sassoon Trophy comes to light because in 1933 he presented another trophy, this time for photographic skills. As reported at the time:
The Sassoon Photographic Challenge Trophy
The entries for the photographic trophy presented by the Right Hon. Sir Philip A. G. D. Sassoon, Bart., G.B.E., C.M.G., M.P., Under-Secretary of State for Air, have now been judged. Eleven units entered for the competition....
1. Andover
2. Bicester
3. Farnborough, No. 4 (A.C.) Sqdn.
4. Bircham Newton, No. 35 (B) Sqdn.
5. Cattcrick
6. Old Sarum
7. Manston
8. Bircham Newton, No. 207 (B) Sqdn.
9. Upper Heyford
10. Abingdon
11. Boscombe Down
In the event Andover won the trophy.