Blackcastle was a small town in England.
In 1980, Beep the Meep crashed his neutron drive star cruiser into the Blackcastle steel mills. He was later found by Blackcastle residents Sharon Davies and Fudge Higgins. The Fourth Doctor learned of the crash and travelled to Blackcastle to investigate. The town was sucked into a black hole when Beep attempted a star jump, but the effect was only temporary as the Doctor had reduced the power of the ship's engines. (COMIC: The Star Beast)
The Doctor returned Sharon to Blackcastle after she had travelled with him for some time. However, she was now aged to adulthood and was uncertain she wanted to go home, but before they could leave the TARDIS, they were transported aboard Varan Tak's ship. (COMIC: The Collector)