Can an employer and/or its employees be liable for harassment on the grounds of sexual orientation where the harassers are mistaken about their victim's sexuality?

Under the Equality Act 2010, harassment related to sexual orientation is prohibited, regardless of whether or not the perception of the perpetrators that someone is of a particular sexual orientation is correct. The employer will be liable unless it has taken all reasonable steps to prevent the harassment. The individual employees will also be liable, whether or not the employer has a reasonable steps defence, since they will be deemed to have knowingly aided the act of the employer.