I misunderstood "board" as blackboard and thought that a Cambridge student had written a proof that, for any arbitrarily wide blackboard, there was a sequence w

I misunderstood "board" as blackboard and thought that a Cambridge student had written a proof that, for any arbitrarily wide blackboard, there was a sequence which it was impossible to write on the board. This seems like the sort of theorem that a college student might be inclined to prove.