 Complete the following phrase:  By the end of April 1942, Barron had completed 39 missions, 29 as aircraft captain, and finished his first tour. Now a pilot officer, having been promoted earlier in the year, he was awarded the Distinguished Flying Medal DFM the following month, the citation noting that Barron was most reliable, efficient and courageous, pressing home his attacks regardless of opposition. It was typical for aircrew that had completed a tour to be rested and perform instructing duties for a time. In Barrons case, he was posted to No. 1651 Conversion Unit, stationed at Waterbeach, as an instructor. After a period of leave, he arrived at Waterbeach on 21 May but within a week was called back to No. 15 Squadron to fly in the 