Deborah Castle

 (nee Gordon), also known as Debbie, was a teacher in the 20th century.

Biography
Deborah once taught Miranda Dawkins and played a role in keeping her safe from Ferran. She was also briefly the eighth Doctor's companion. She spent several days in transit with him across the globe to steal the Atlantis. They used it to rescue Miranda, who was in a spaceship in Earth orbit. Though a stowaway, Deborah was nevertheless one of the few Britons to fly on an American spacecraft. (EDA: Father Time)