21.5—(1) If the court has not appointed a litigation friend, a person who wishes to act as a litigation friend must follow the procedure set out in this rule.
(2) A person authorised under Part VII of the Mental Health Act 1983 must file an official copy(GL) of the order or other document which constitutes his authorisation to act.
(3) Any other person must file a certificate of suitability stating that he satisfies the conditions specified in rule 21.4(3).
(4) A person who is to act as a litigation friend for a claimant must file—
(a)the authorisation; or
(b)the certificate of suitability,
at the time when the claim is made.
(5) A person who is to act as a litigation friend for a defendant must file—
(a)the authorisation; or
(b)the certificate of suitability,
at the time when he first takes a step in the proceedings on behalf of the defendant.
(6) The litigation friend must—
(a)serve the certificate of suitability on every person on whom, in accordance with rule 6.6 (service on parent, guardian etc.), the claim form should be served; and
(b)file a certificate of service when he files the certificate of suitability.
(Rule 6.10 sets out the details to be contained in a certificate of service)