2 minutes after this post came another stating 11 Oct 1984 which I am inclined to agree with as the next batch of photos includes my daughter at Christmas 1984. This picture would most likely have been taken the following day, Friday 12th October, in the late morning, and a comment from another user here suggests it most likely started from Euston and joined the main GW line at Acton. The first coach does not appear to be Mk 3.
The very next photograph I took shows a class 56, 56065, on another passenger train from the London direction, will add a link here showing the coaching stock type. [url]https://www.flickr.com/photos/56186958@N05/33852849375/in/datetaken*********[/url][/QUOTE]
I am very certain that I saw The Clansman at Paddington and I do clearly remember seeing Inverness displayed on the main departure board (and that it was a weekday) so I'd strongly believe that any Euston via Acton workings would have been at the weekend. However of course I can't say anything for 100% certain and it doesn't help that I didn't have time to go and see what was on the front of the train as I had to get to work!
EDIT: I think this is the departure board in use at Paddington at the time although the photo is from 1985:
[URL="https://www.flickr.com/photos/15977833@N07/6042705431"]https://www.flickr.com/photos/15977833@N07/6042705431[/URL]