Thin Ice follows the well-established convention of taking the new companions back to the past within their first three adventures. Rose and Martha went to Victorian England, Donna to Pompeii, Amy to the Second World War and Clara to the 1980s. This time around, Bill continues her TARDIS induction with a visit to London’s last great Frost fair in the pre-Victorian Regency period.
After making so much effort to dress for the period, Bill is understandably concerned that the TARDIS will stick out like a sore thumb in 1814.
“You’re species hardly notices anything,” replies the Doctor dismissively.
He clearly doesn’t understand his fans, who will no doubt be pouring over every last detail in the latest episode, looking for clues to future storylines and making links to Doctor Who’s own past.
Bill continues to ask the Doctor some fundamental questions, throwing up a few old chestnuts in the process, and once again, the ongoing mysteries of the Vault and Nardole are relegated to footnotes as the series continues to build on the relationship between her and the Doctor.
But nevertheless by the end of the story, that vault is once again demanding our attention.