Theory:Doctor Who television discontinuity and plot holes/Kerblam!


 * Runaway Bride established that entering the TARDIS is impossible unless connected to the TARDIS (like those particles in Donna) or the Doctor materialises around the object (as showcased in The Parting of the Ways,). So how does the 'Kerblam!' postman teleport aboard?
 * A junk mail robot does it in The Greatest Show in the Galaxy. Runway bride broke continuity, not this. And perhaps the shields were up.