This is definitely an unusual Class 165/166 combination! Two car 165128 has been strengthened by the addition of centre coach 58609 from 166209, made all the more obvious by the interloper's different livery. It is pictured passing Hinksey on 20 January 2016 with the 2P60 14:37 Oxford to Paddington GWR service, running with 166220. Interestingly, I also have a photo of this same pair in a more conventional guise, taken a few years earlier.