(20 Feb 2016, 3:11 pm)Jimmi wrote Only other possibility could have been it was on the 11:52 running late. The 13:22 from Durham (which would have been the 12:07 from Darlington) was 1513 when it passed through Newton Aycliffe at 14:06. 1522 was the working behind. Changeover somewhere on the route perhaps?
Maybe Harrowgate hill? Explains the 49 minutes late one??