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.
[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.