Jill Manson was portrayed by Juliet Harmer.
Jill is an operative of a unknown foreign force slowly infiltrating a village at the coast. Her organisation replaces villagers one at the time for their spies. Pretending to be a headteacher she is part of the undercover operation that kills anyone that finds out the truth. She welcomes Mrs Emma Peel (Diana Rigg) and Mr John Steed (Patrick Macnee) when they visit the village. She learns Mrs Peel is a new teacher at her school.When she and the other conspirators learn that the pair had discovered their secret they start to look for them. When they find them a big fight breaks out. Jill fights Peel fights Peel in single combat. In a intense struggle Jill reverses Peel by yanking her hair. Jill uses multiple holds and locks and nearly overcomes Peel. However Peel manages to get the better of her by twirling her around several times and releasing Jill against the wall. She bumps her head against the wall, which causes her to be knocked out.
Even while feigning to be a villager Jill appears cold and distant. Part of a ruthless organisation she has no trouble eliminating anyone that poses a threat.
Jill is a highly skilled fighter. She was nearly able to defeat Peel who is a master of martial arts. During their fight Jill reversed a hold by seizing her hair and instantly trapped her in a stranglehold. She attempted a huge variety of holds and locks against Peel before she got defeated.