Video from Watford Junction in summer 1991 seems to show two (presumably northbound) night trains:
The first one is at around 4:15, hauled by a Class 87 and has a pretty weird formation of 2 Motorail GUVs, 3 SLE/SLEP, 1 TSO, 2 BSO with the van areas facing each other, 2 TSO. Strangely large...