Daniel: "This is my grandfather (Rev. John W. Morris) in the Dumfries area of Scotland tampering with his motorcycle and sidecar. The photo dates from about 1926-ish."
-JdK- This looks like a Model Big Four Norton with a 'De Luxe' sidecar attached. SM3818 would have been issued by Dumfries C.C. (currently Carlisle (Dumfries)).
-Martin- SM3818 dates from as early as mid-1923