1976 (if you look at the '
uncropped' version [found via Google 'Search by Image' function] - if you scroll down the page that is linked it shows, I think, the jubilee radome paintwork mentioned above - although the '77' in 1974 is a bit confusing!)).
Curious why they all appear to have the same tail letter (R) - they have different nose numbers. Is/was this a FAA thing?