Wheel out, top nut in a vice with the frame upside down and a thick length of wood down into the fork crown and turn the wood. Use the crown to lever against not the fork blades.
A few Tom Avon badged short wheelbase TT frames were about at the same time as Alf Engers (errr, and me)
Very short rake forks and fag paper clearances quite Aende looking.
The ones I came across were real beauties like this one :)
That's what crossed my mind for a 1987 headset unless NOS. I wonder if the races show some brinelling (OK, that's the wrong term I know but everybody uses it)