[Jon]

Bann flew with Yellow Section so very probably was involved in the second D017 claim, interestingly his letter states that he flew with the CO and another (Batt?) on the day he was shot down, and was pleased on his return from bailing out three days later to hear that the other two "got a German"
Interesting that Sgt Batt did not mention a Hurricane being lost, is it not possible the report was filed straight away on return before he was aware of Sgt Bann being lost and not simply landing at another airfield? On reading Squadron ORB's I have seen on several occasions where pilots have got lost or seperated for them to return home alone, maybe Banns non arrival was nothing out of the ordinary in that summer of 1940.
Sgt Bann himself on 25 July landed back early having lost his section in cloud.
The 21st July still looks the more likley, certainly no later than this date, do any other dates fit?