Not sure it's the same chap:
Squadron Leader David Butler DFC who joined No 12 Squadron on 19 June 1943 and took part in the raid on Hamburg on the 24/25 July 1943 as rear gunner on Lancaster ‘PH-K’. Having completed his first tour in February 1944 he was awarded the Distinguished Flying Cross. His second tour was with No 171 Squadron with Halifax aircraft
http://www.aviationcollectables.co.u...mfseries1.html