Hi Drew, thanks for that. From what I've seen of the Tunnelling companies war diaries they would appear to overlap as a Lt Brandt appears in both the 170th & 173rd. I'm going to do a timeline on both today to see if there are other overlaps. I would imagine that the actual formation of the 170,171,172 &173 in April/May 1940 was a bit confused . From what I've read so far I believe that my father must have been with the section that was left in Douai under Major Foss which was actually embarked from Dunkirk.