37800 Cassiopeia passes the Brookfurlong Farm footbridge, near Islip, on 2 December 2021, running as the 12:44 Bicester MoD to Derby RTC light engine. The loco had travelled down to Oxford the previous day, and then to Bicester earlier this morning, in preparation for the 5Q42 10:30 Bicester MoD to Crewe South Yard ECS. When it became clear that it was heading back the way it come light engine, I decided to stick it out, as it is such a long walk to get to this location, and at least the lighting was perfect!