How's this for first generation DMU flexibility? A Class 121/108/117 combination passes Shottesbrooke on 5 September 1992 with the 2A33 09:12 Reading to Paddington Network SouthEast service. Class 121 55029 (L129) has been temporarily formed into three car set L429. That set number was originally allocated to one of Reading's Class 117 sets (51367 59519 & 51409), but only the last vehicle of that combination remains here. To add to the variety, the centre vehicle is Class 108 54495. Class 121 'Bubble Cars' often substituted for the DMBS vehicle of a 117 unit on an ad hoc basis, but this is a slightly more permanent arrangement, as the 104/117 set, although made up of two driving cars, would not have been used on its own, as neither is a brake vehicle.