From the 21 Squadron ORBs:

" 5.7.43 Weather Fine Visibility Good - Exercise 'Eve'. Eleven aircraft flew at 10,000 - 15,000 feet. There were quite a lot of interception by defending aircraft."

Take-off time was 13:10, flight was two hours, forty-five minutes in a Ventura bomber.

Does anyone know what an "Eve" Exercise was?