Thanks for posting the photo. My father, Bill Williams, is the one without the brevet, one from the left. The unknown Wing Commander, one on my father's left is OC either 50 or 61 squadron and the photo is probably taken at Skellingthorpe. 40 missions is a lot. 50 and 61 Squadrons together had around 40 aircraft that made 50 or missions. That's a lot of numbers!