A Good Man Goes to War
The Doctor mentions that he has attended Frost Fairs before. In "A Good Man Goes to War" (2011), River Song says that the Eleventh Doctor took her to the 1814 Fair for her birthday, where they were serenaded by Stevie Wonder. The First Doctor took Vicki and Steven to the 1814 fair in "Frostfire", where they encounter Jane Austen. The Twelfth Doctor took Clara Oswald to a frost fair in the 1890s in the novel "Silhouette", after promising to take her to one of them in "The Caretaker" (2014).