Howling:E-Space and inter-dimensional travel

It's been said that before the Time War, the Time Lords could easily travel to and from different universes and dimensions across the multiverse. In "The Edge of Destruction", the First Doctor and his companions briefly observe a planet in another universe. But then there's the E-Space arc, where the TARDIS accidentally falls into a different dimensional plain and is stranded there for a while. Any ideas as to why the Doctor would find E-Space more difficult to escape from than he would any other dimension? EJA 16:30, May 5, 2011 (UTC)