Complex sentence: When it was his turn to be conscripted, Purdon's National Service number ended in 0, which meant that he would not be joining his brother in the army-he was bound for the pits (coal mines).
Split into simpler sentences: When it was his turn to be drafted, Purdon's conscription number ended in 0, which meant that he would not be joining his brother in the army. He was bound for the pits (coal mines).