Wyckham

Miss Wyckham was a German spy who posed as a schoolteacher in England.

On 7 June 1941, Miss Wyckham met one of her pupils, George Woods, along with Clyde Langer on their way to alert the Home Guard. She told them the whole village had been surrounded by Germans. She had a gun with her.

Wyckham pretended to help the boys capture the Nazis in the church, but revealed that she was a double agent. She fled with Koenig and the other Nazis when George and Clyde took the Chronosteel from their weapon, a device for avoiding radar. The Nazis fled to the beach but were taken prisoner by the Home Guard. (TV: Lost in Time)

Behind the scenes
While not elaborated in the story, as a British citizen who aided the Nazi forces, Miss Wyckham would have likely been executed for treason.