My copy of Russell Meiggs’ The Athenian Empire (reprinted 1975) contains two (numbered) tickets to a lecture on ‘The story of three Roman sites saved for the nation’. This was a lecture hosted by the Welwyn Archaeological Society in the mid to late 1970s (and with a tpq, I suspect, of 1975). I would imagine one of the sites was the Roman bath-house under the A1(M) at Welwyn.
Can anybody provide a little more information?
Heritage Futures 
This is a ticket to a day conference held in 1979. It would have been organised by Tony Rook, then director of the Welwyn Archaeological Society, and the art work is his too. An extract from the late Merle Rook’s diary says: “Conference at Civic Centre. Brian Philp’s train was late and I couldn’t get out of the drive as a lorry had parked across it. Mrs Mac [MacTaggert] did the tea which was late and weak and we had queues of people waiting.” Hope this helps. Kris Lockyear (current director of the Welwyn Archaeological Society).
Thank you for identifying the date. I do not remember anything about the tea!