From TARDIS Index File, the free Doctor Who reference.

Carbury was a small English village located near Lake Vortigern. It was located within helicopter range of London.

The Carbury Historical Trust, under the direction of archaeologist Peter Warmsly, maintained an extensive archaeological dig near the lake: an 8th century battlefield, believed by Warmsly to have been the site of the Battle of Camlann, the final apocalyptic battle between King Arthur and Mordred.

Husband and wife innkeepers Pat and Elizabeth Rowlinson maintained a small hotel, the Gore Crow Hotel, with a pub frequented by Carbury locals, including Warmsly and a young woman named Shou Yuing. The Doctor and Ace stayed at the Gore Crow when they visited Carbury on the trail of an interdimensional distress signal. (DW: Battlefield)

Behind the Scenes

Though Ireland has a town of this name, the setting of Battlefield is fictional, as is Lake Vortigern. Most Arthurian tradition places the Battle of Camlann in either Wales or Cornwall. One possible English site of the battle is located near the Somerset village of South Cadbury.