There is a proposition that Alperton to Mornington Crescent can be achieved in four moves. However proof has not been accepted for the existance of this number.
*peers closely at this for some days* I have only one comment; it's just a passing comment, I don't think it affects anything, but perhaps our learned friend could clarify: Playing a Zone 1-6 Travelcard explicitly revokes everything northwest of Moor Park, which is fine, but I'm interested in the position of the Chesham spur at peak times. How does this affect the freem around Aldgate East? Just asking.
[Watty,PW] Oh dear, Paul, I do believe Watty has spotted the flaw in your otherwise excellent and cunning plan. The freem count will be negative at Aldgate East as Watty surmises and so Finsbury Park will be in close jeopardy, and thus unplayable for three moves minimum. Darned close though.