Indeed Ade, this London Gazette malarkey is pretty good!
Just found a bit more info on our boy. He didn't rejoin at the outbreak, but rather in 1910 after a break from the Army of 3 years. It seems civvy life didn't agree with him. I'm itching to find his wartime records now!
Also this one gives up his full name for the first time. William Dillworth Crewdson.
And here, his pre war promotion to Captain in 1913 is noted in the Borders list of Officers for the 4th battalion.
4th Battalion, Border Regiment Army List 1914 - Border Regiment Wiki