First appearances of Sarah Jane Smith and The Sontarans.
Introduction of new opening and closing credit sequence featuring the camera slit-scan time vortex effect and the first appearance of the diamond Doctor Who logo. The logo would be used until 1980, but would reappear in 2023.
This serial takes place in England in the 13th Century, making it the only Third Doctor serial set in a historical context, which had been a common feature of the series in its early years.