"A person discriminates against another in any circumstances relevant for the purposes of any provision of this Act if - (a)... (b)he applies to that other a requirement or condition which he applies or would apply equally to persons not of the same racial group as that other but - (i)which is such that the proportion of persons of the same racial group as that other who can comply with it is considerably smaller than the proportion of persons not of that racial group who can comply with it; and