I’m 99% sure that one of them is Sebastian. Pretty sure I’ve read something confirming this.
The other one is a little more ambiguous, but I think the cloth reads 9, which would make him Andy Pandy. The loose horse also appears to have a very small star on his head, which marries up with Andy Pandy (the 1977 Whitbread offers better viewing of his finer features).
So the two (admittedly) loose horses who beat Rummy home that day both fell at Bechers when leading. It’s easy to forget how fortuitous that third win was when you consider the two falling leaders mentioned, Boom Docker’s bizarre refusal at the 17th when well clear of the remainder, Sage Merlin’s fall at the Chair who was Boom Dockers main persuer at the time and himself quite a way clear of the others (though his rider once replied to a comment of mine on Facebook that he was all out at the time!), and of course the shuddering mistake by Churchtown Boy at the second last.
You could write dissertations on some of those old Nationals. Wonderful stuff.