66121 finds a gap in the procession of early morning HSTs to lumber slowly up the Great Western Mainline at Compton Beauchamp with the 6D09 06:43 Avonmouth to Didcot Power Station coal train on 14 April 2008. It will no doubt be put onto the relief line at Challow to allow following First Great Western services to pass. The extra wide trackbed here is a clue to the fact there was also an up relief line at this point in steam days, extending from Shrivenham to Knighton Crossing.