66186 takes the relief line at Challow on 19 September 2012 with the 6M26 07:36 Westbury to Stud Farm ballast empties. This was following a mere five minutes behind the regular 6M50 07:36 Westbury to Bescot service, on this occasion hauled by 66167. Note the physical impossibility of both these trains running to time, as they are booked in the same path!