I am not altogether convinced that this is the right Arthur. It is self consistent up to 1911 census, but the 1939 Regiister puts it in doubt. It i certainly the correct marriage, so it the DOB that is in doubt, common for the RIC records of this time
1884 Sep 26 born Derby
1891 census at Litchurch, Derbyshire,
1901 census at 18 Shaftesbury St, Derby
1902 Mar 3 Enlisted in KRRC. Parents Thomas & Ann . 18 Shaftesbury St, Derby. Brother George
1904 May 17 discharged medically unfit
1906 Aug 6 married Derby to Annie Elizabeth Green
1911 census at Derby
1921 Apr 26 enlisted with RIC no 80739. ex-Soldier & Painter's Assistant
1922 Jan 19 Disbanded
1939 Register at 76 Marlborough Road, Derby, with wife Florence. He is Furnace Hound
or
1939 Registrer at Derby with Annie Elizabeth