The song sung in the pub by H division is The Trooper Cut Down in His Prime by Ewan MacColl and Peggy Seeger, which was not released until 1960, well after the time frame in which these events are set. While the song is based on The Unfortunate Lad or The Unfortunate Rake, known from at least 1850 on and the basis for many variations, the lyrics sung here are indeed those written by MacColl (with a couple slight variations from earlier versions).