Alistair Carson was a 52nd century Time Agent, who under the leadership of Natalia Goldsteed, was sent back in time to the beginning of the First World War under the disguise of a member of the War Office carrying classified and confidential documents.
Biography[]
The documents in which Alistair was carrying had been purposefully sabotaged and were in fact the details of the Second World War. If he had played along and sent the documents over to the official British government figures, history would have been completely torn apart. The Sixteenth Doctor with her companions Alec and Constance O'Conor met Alistair onboard a train from Truro, Cornwall to London, discovered what was happening and abruptly put an end to it. (TV:The Timeless Train)
It was later revealed that Alistair Carson was also working under the Eighth Master, as well as Natalia, and was subsequently killed for his failure shortly after the Doctor's, Alec's and Constance's departure from Truro. (TV: Spiders and Fireworks)