An undercover police officer who deceived a woman into a five-year relationship and strung her along when she wanted to have children with him had “sadistic tendencies”, the spycops inquiry has heard.

Mark Jenner lived with the woman, known as Alison, as a couple without telling her that he was an undercover officer sent to spy on political campaigners.

He then disappeared from her life after feigning a nervous breakdown. She discovered his true identity only after years of her own detective work.

Giving evidence on Monday, Alison, a leftwing activist, said Jenner had shown “sadistic tendencies” in his treatment of her that left her devastated.

He was given a commendation by his superiors for his covert deployment.

Alison testified at the inquiry, which is examining how about 139 und

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