Samantha Briggs was the sister of Brian Briggs.
When Brian disappeared on a Chameleon Tours trip to Rome, she travelled from her home in Liverpool to Gatwick Airport to investigate. On 20 July 1966, she teamed up with the Second Doctor to find the other missing persons and defeat the Chameleons. (TV: The Faceless Ones)
In his investigation of reports of a series of agent provocateurs known as "the Doctor" who had been involved in numerous unusual incidents, the journalist James Stevens interviewed Samantha about the Gatwick Incident. She described the Doctor as "a short man with a mournful face and dishevelled clothing." She also noted that he had a "blurred" English accent which defied description and seemed to be extremely knowledgeable on a wide variety of subjects. Stevens dubbed him "the Gatwick Doctor" due to his involvement in the investigation of holiday fraud. Furthermore, Samantha told Stevens that the Doctor was accompanied by "a young Scots lad in a kilt, called 'Jamie'". (PROSE: Who Killed Kennedy)
Samantha was seen as very headstrong, preferring to take action rather than wait for help, such as when she refused to sit and wait around for the Doctor and Detective Inspector Crossland to find any traces of her brother in Gatwick Airport.