Thanks for your interest. Yes, this is the badge, it is the largest one of the set, as I read the article on the link you so kindly provided it did confirm that this medal was first issued in the Great War but also went on to say that the First World War medals were numbered, this one isn't so I presume this is my fathers rather than my grand-fathers.
This now raises another question!! Why didn't my Grand-father, who was injured, captured, released then discharged in 1916 receive one. Did he not possibly meet some criteria to receive one???
If it is of any further help my father was ;
Walter Markham, service number 1430589
Grandfather was Walter Markham, service number 7555