It's Signals code from the time of WW1 - so ack ack = AA = anti aircraft, PM was Pip Emma, a despatch rider = DR was usually referred to as a Don R and Talbot House the charity started near Ypres in WW1 was ( and still is) called Toc H - there must be a full list somewhere but because it was superseded by systems such as Able, Baker, Charlie, Dog (US) and Alpha, Bravo, Charlie, Delta (International) it's largely forgotten apart from crosswords and Lord Peter Wimsey novels.