From a reader in Belgium:

Mr. Derbyshire—Whether farmers in Picardy are still finding unexploded munitions from WW1, i don’t know. But in the Belgian ‘Westhoek’ (area around Ypres – Dixmude, Flanders Fields in other words), around 3.500 pieces of munition are found and cleared every year (150 tons), a significant number of them filled with toxic contents. See here.

[Derb] Amazing. One of those might have been aimed at my Dad.