I was on a tour around then, Sarah did a series of trips starting at Wembley Park, running to Uxbridge, where she got herself gapped, Amersham and Watford. Can't remember the precise routing but the speed down Chorleywood Bank was interesting. It was a cool day and the stock was of course unheated!!
I fully expect that someone will be along soon with the full details
Sarah also took the inter-city stock round the Circle during that time for gauge testing. There's a mention of it on here somewhere posted by myself and contributions by Bigal who was station inspector at South Kensington at the time.
Page 316 of Underground News, June 2015 edition, talks about this tour.
No name is mentioned for the tour - it seems to have been one of the annual tours which were run in those days. Would be great to see it happen again, although perhaps the carriages would have to come from a museum / heritage railway rather than a TOC.
The carriages were Mklld and Mklle from BR Eastern Region.
I recall seeing this tour train, and have a little super 8 cine film of it.