went to Oxford on business today and thought hey there’s that train I’ve been driving since August! But, disappointingly when I got close it was a 165 not a 166 but not sure what the differences are. Anyway it was nice to see something similar, and for a Northern lad, something in GWR livery for the first time in the flesh
165's are far more common than the 166's. Although they are very similar the 166's are faster and have air conditioning. To this day I still can't tell them apart without looking at the unit number.