No. All HST second class coaches - and loco-hauled Mk3s for the West Coast - were originally built with a 72-seat layout, as shown on this diagram, labelled TS original
http://www.rmweb.co.uk/community/uploads/monthly_11_2010/post-7112-014695300 1289837487_thumb.jpg
Ah great thanks for that. I vividly remember travelling from Newcastle to Peterborough around '78 ish as an infant in stock that was entirely table seat, which would suggest to me I was on a loco hauled train.?