My father was in Brian Wickham's 7 Squadron Valiant crew that won it in 1960. Here is what I discovered in 7 Squadron Operations Records Book at the National Archives, Kew:
(from AIR27/2728)
1-3.5.1960. 7 Squadron won Bomber Command navigation competition, the Phillip Sassoon Cup. The average error was 4 miles beating the next best by 2 miles. They are the only RAF squadron to beat the competing USAAF 6th in any field.
The best individual score in the whole navigation competition was Wickham's crew with an error of only 661 yards, being awarded individual praise.
Wickham's scores were:
Bombing 183 points position 41st
Navigation 99 points position 1st
Combined 282 points position 21st
7 Squadron was 5th in the bombing competition and 2nd overall.
(Additionally, on 13-17.6.1960 During Exercise Sunspot, Wickham won Moss Bombing Trophy with an average error for his best 6 bombs of 107 yards from 40,000'. The trophy was named after F/L A J R Moss in 1923 and was last competed for in 1932.)
This is the trophy each crew recieved:
It's a bit battered and missing the 7 Squadron badge.
This is the programme from that event:
Strangely it does not give a list of previous winners but it says the following about the Sassoon Trophy:
This trophy was presented to the RAF in 1953 by the Right Honourable Sir Phillip Sassoon, Bart., Under Secretary of State for Air, for competition between squadrons of the Wessex Bombing Area of the Air Defence of Great Britain.
The trophy was originally presented for an annual 'long distance' competition between night bombing squadrons. In 1951 it was competed for by H2S equipped medium bomber squadrons in a combined 'blind' bombing and navigation competition. In 1952 the trophy was awarded to the best squadron in Gee-H bombing and was won by No 12 Squadron. The trophy was not awarded again until 1957 when it was reallocated for competition as the Navigation Trophy for the Medium Bomber Force. It was won that year byNo 83 Squadron flying Vulcans, and in 1958 by No 138 Squadron in Valiant aircraft. The winners in 1959 were 617 (Vulcan) Squadron.
This is the trophy:
Other trophies mentioned in the programme are the Laurance Minot Trophy and the Aramaent Officer Trophy.