I would also like to add the Five Doctors written by protean, script editing, scifi Yoda, Terrance Dicks. Partly because it started with that brilliant quotation by Bill Hartnell, partly because it introduced that amazing console room and partly because of Tony Ainley's frankly brilliant portrayal of the Master. 90 mins, Five Doctors, Gallifrey, The Castellan. How did I not include this in my original list of three?
Ahh, but Chris - which version? The original, the rejigged "new effects honest gov" version or the (gasp) fanw@nkery "6" Doctors which splices in Time Crash & some more Tom Baker footage?