An authority are not required to grant, or arrange for the grant of, a tenancy to a person under section 554 or 555 unless he requests them to do so in writing before—
in the case of an acquisition under Schedule 20 (repurchase,), the service on the person entitled to assistance of a copy of the agreement drawn up under paragraph 5 of that Schedule, or
in the case of an acquisition in the circumstances described in section 549(3) (acquisition in pursuance of right of pre-emption, &c.), the time of the disposal.
An authority receiving a request under subsection (1) shall, as soon as reasonably practicable, give notice in writing to the person making the request stating whether in their opinion either of the Cases in section 556(1) applies (cases in which tenancy may be of a dwelling-house other than the current dwelling-house).
If their opinion is that either Case does apply, the notice shall also state which of the Cases is applicable and the effect of section 556.