Doctor Who: Shadow of the Ice Warriors part four

Those still in the court fear the oncoming Ice Warriors: with cryo-grenades primed for devastation, Ice Lord Valtarr will stop at nothing to succeed in his mission, even if it means destroying everything in his path. But Viggo is just as much of a threat: with his murderous intent now clear, what will the Doctor think of his ally?  Battle lines are drawn, with the fate of Denmark up for grabs. Who will be on the winning side? And will the Doctor make the right call?