Yanks in British Commonwealth Forces in the Great War

[Sir William]

Does anyone know of any Americans who served in the British, Canadian or Australian Forces during the FIRST World War?

I know that a small number of Americans joined the British Forces, usually via Canada, in the Second World War:

17 served as officers in the King's Royal Rifle Corps (the old 60th Royal Americans)

Probably 100 or so in the RAF or RCAF (and not just in the Eagle Squadrons - I knew someone who was in Fairey Battles and Vicker Wellingtons).

Perhaps 6 or so in the Royal Navy.

I know of at least one man, Arthur Empey who served in the ranks in the Royal Fusiliers during the First World War, but I'm not aware of any other Americans who served in British (or Canadian or Australian) uniform during the Great War.