An interesting picture. The topic of interlopers on Southern metals comes up with monotonous regularity on the SEmG Yahoo message board and the same answers get trotted out every time. Here we see Churchward 4300 class mogul No. 6313 of 1921 vintage on the company of some pre-grouping, probably of LSWR origin, service stock at Fratton mpd on 12/9/49. According to my allocations source 6313, which had until recently been a Reading based engine, had by this time been transferred to Oxford mpd.