Thanks d_m. I re-read eightf's post and went a-trawling the internet for info on 1960s a/c EMU▸ 's. I wonder what delightful fare the 'griddle cars' cooked up?
Remember it well I had a girl friend in Braintree at the time, one advantage of being a railwayman you could have girlfriends all over the place and visit them cheaply!
So my trips to Braintree were mostly to sample the grilled steak the Griddle Car produced. A real piece of steal cooked to order served in I some form of bap (which I think were new in the South at the time). Delicious. Plus the superb runs to Witham on the 309s. Braintree branch was still
DMU▸ . I have a b/w picture somewhere taken in one of intermediate cabs of the speedo rock steady on 90.
What more could a young lad want?