Is it really 1973? This is the so-called Cambridge Buffet Express. The fourth vehicle appears to be either one of the Gresley buffet cars or the famous Thompson E1706E which appeared on these services around this time - all very grand for what was a short outer-suburban service. The seventh vehicle is still in maroon livery. There were two of these buffet sets, one based at each end of the route, with the other King's Cross - Cambridge services mainly in the hands of DMU's or rakes of loco-hauled suburban stock.