(1) A person (A) discriminates against a disabled person (B) if—
(a) A treats B unfavourably because of something arising in consequence of B's disability, and
(b) A cannot show that the treatment is a proportionate means of achieving a legitimate aim.
(2) Subsection (1) does not apply if A shows that A did not know, and could not reasonably have been expected to know, that B had the disability.