Isn't the rope so he can drop into the tardis as it's on it's side?? Looks like it could be a funny scene.
In "Time Flight" (a fifth Doctor Story) the TARDIS is put on it's side in the cargo hold of Concorde. The Doctor gets in, and flicks a switch and the internals swing around so that it's right way up even though the external Police Box is on it's side. Of course this was back when you rarely saw through the door to the outside world, unlike now.
Two things make me think that won't happen this time round: a) it originally happened in Time Flight (which was crap and therefore should be wiped from history), and b) the TARDIS is damaged and so that system probably doesn't work anyway.