A friend has asked me for information about his great grandfather who died in the Great War. He was Pte Robert Armstrong 42414 of 20th(Wearside)Bn Durham Light Infantry. He died on 21.09.17 and is buried in the Hooge Crater Cemetery. I have obviously gone to the CWGC site and looked at the Long Long Trail but don't have access to Ancestry. Can anyone give me any more info on him please or the actions of the battalion when he died. Thank you for your time.