Perception harassment
[ch 6: page 172]There can be unlawful harassment where an individual mistakenly believes a person has the protected characteristic, for example, where a man is harassed because he is mistakenly thought to be gay.
There can be harassment even though the offensive conduct is not because of a protected characteristic, but is simply related to it. For example:
A female worker has a relationship with her male manager. On seeing her with another male colleague, the manager suspects she is having an affair. As a result, the manager makes her working life difficult by continually criticising her work in an offensive manner. The behaviour is not because of the sex of the female worker, but because of the suspected affair which is related to her sex. This could amount to harassment related to sex.
EHRC Code of Practice on Employment
www.equalityhumanrights.com/sites/default/files/documents/EqualityAct/employercode.pdf