Sgt Eric Bann, 238 Squadron - Shot Down 21 July 1940?

[Peter Cook]

I am trying to establish when Sgt Eric Bann of 238 Squadron was shot down into the Channel during the Battle of Britain. According to Brian Cull's Battle for the Channel Pg. 233, he was shot down on 21 July, and Cull quotes from a letter from Bann, reproduced in Battle of Britain Then and Now, Pg. 352. The aircraft's serial number is not identified. However, there is no date on the letter and it is located in BoB Then and Now alongside RAF casualty listings for August 12. Patrick Bishop reproduces part of the same letter, in his BoB book, pg. 113, but adds the date of July 19. I can find no record of Batt being shot down in either July or August in the Form 540 and 541 ORB records for 238 Squadron, and his biography in Wynn only describes Bann being shot down once — on September 28, when he was killed. Can anyone shine a light on the correct date and circumstances for when Bann was shot down into the Channel?