I doubt the M3 or indeed the M25 were shut for its arrival, though perhaps they chose to delay trains on the Waterloo/Portsmouth line which is right off the northern end of the runway.
From memory the M11 was closed briefly for a Duxford arrival or two in the past (B-52? VC-10?), which may be what you are thinking of? They squeezed Concorde in just before the runway was truncated by the motorway works in the mid-1970s.
Last edited by treadigraph; 13th Jul 2012 at 07:01.