Penultimate episode in what critics are saying has been one of the best series of Doctor Who to date. Tonight, the Doctor faces the greatest challenge of his many lives when he is trapped, alone, in a world unlike any he has ever seen. Pursued by a fearsome creature known only as 'the Veil', the Time Lord must attempt the impossible in one final test, and if he makes it through, the long-lost world of Gallifrey is waiting. Peter Capaldi takes centre-stage in what is effectively a one-man episode for the first half of this year's series finale.