employment practice which operates to exclude [black people] cannot be shown tobe related to job performance, the practice is prohibited …

Congress directed the thrust of the Act to the consequences of employment practices, not simply the motivation. More than that, Congress has placed on the employer the burden of showing that any given requirement must have a manifest relationship to the employment in question.
3 THE ELEMENTS OF INDIRECTION DISCRIMINATION Equality Act 2010

19 Indirect discrimination

(1) A person (A) discriminates against another (B) if A applies to B a provision, criterion or practice which is discriminatory in relation to a relevant protected characteristic of B’s.

(2) For the purposes of subsection (1), a provision, criterion or practice is discriminatory in relation to a relevant protected characteristic of B’s if—

(a) A applies, or would apply, it to persons with whom B does not share the characteristic,

(b) it puts, or would put, persons with whom B shares the characteristic at a particular disadvantage when compared with persons with whom B does not share it,

(c) it puts, or would put, B at that disadvantage, and

(d) A cannot show it to be a proportionate means of achieving a legitimate aim.

The formula consists of the following elements: (1) an apparently neutral provision, criterion or practice (‘PCP’), (2) which puts, or would put, (3) the claimant and the claimant’s group at a “particular disadvantage”, and (4) cannot be justified (para.(d)). The group is defined by its ‘protected characteristics’, but does not include ‘pregnancy or maternity’.
(1) Provision, Criterion or Practice
(a) Subjective Decision Making

Watches of Switzerland v Savell [1983] IRLR 141 (EAT): ‘…vague, subjective, unadvertised promotion procedure which does not provide…any adequate mechanisms to prevent subconscious bias unrelated to the merits of the candidates…for the post….’
(2) Proving a Particular Disadvantage
(a) Choosing the Pool

Equality Act 2010, s.23(1):