EMT are using GBRF class 66's so it could be one of themPast Doncaster Roberts Road shed earlier today, was unable to see exactly what locomotive it was because view was obstructed and could only see roofline,it wasn't the usual 66's or 67's.
I think this could be the associated RTT entry for the move :- http://www.realtimetrains.co.uk/train/R03700/2018/03/23/advanced