"subtle tributes to the 60's" - and Edward Burnham

Apologies if you have been waiting patiently for the 12th installment of my Cyber-Odyssey. I was going to post it tonight but I spent so much time documenting the history of London Underground's District Line on my other blog that I ran out of time.
One thing I would just like to mention is something Peter Capaldi said in an interview with Entertainment Weekly - prior to his appearance at San Diego's Comic-Con. When asked about the two-part Series 9 finale - to be directed by Rachel Talalay - he said it contained those subtle tributes to the 1960's? Presumably 60's Doctor Who, as opposed to the decade in general.
Will be interesting to see how subtle these references are.

Also just like to mark the passing of actor Edward Burnham, who appeared twice in the series - playing scientists of varying eccentricity both times. He was Prof Watkins in The Invasion in 1968, and Prof Kettlewell in Robot, in 1974/5. He died on Tuesday 30th June, 2015, at the grand old age of 98. If you have seen his appearances on the DVD extras for both stories, you'll know he was a bit like Kettlewell in real life.