Hi Trish
I have asked him and he does not know the name of his Grt Grandmother unfortunately.
All he had to go on was that Robert G Hutton was in the 10th Batt East Yorks Regt and was killed 1917. we have found him on the CWGC site and he remembers going to his grave in france many years ago. there appears to be a Robert Gargaigue Hutton on ancestry but I do not have access to that. not sure if it is him but the Gasgoine spelling seems to change alot.
the Robert is the one aged 8 in 1901.
many thanks for your help so far
Nick