Matilda (The Comet's Tail)

Matilda was a student in the 20th century.

Matilda studied particle physics. The Fifth Doctor guessed that she had a South African accent.

The Doctor encountered her in a coffee bar when he was trying to reach his bookshop. She seemed to know who he was, as she knew that he liked sugar in his tea.

When the coffee bar collapsed in an explosion, the Doctor and Matilda huddled together, burning in the wreckage. (PROSE: The Comet's Tail)

Behind the scenes
Because The Comet's Tail seems to be a dream of the Doctor's, it is not clear whether Matilda was real or just part of the dream.