The clearest is the 1914 Star, for service in action in the very first months of ww1. Although they are not shown on the form, he will almost certainly have earned the British War and Victory Medals. With the '14 Star they are known as a trio, or Pip, Squeak and Wilfred. Google will tell you more.
He also served in the Anglo Boer war and earned the Queen's South Africa Medal, with clasps for various actions during that campaign, and the King's SA Medal, with clasps.
Best of all is the Distinguished Conduct Medal, details of which should be reported in the London Gazette, available online but with a hard search system.
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