(1) Reasonable force may be used for the purpose of gaining entry to any land
(other than such part of a building as is being used for residential purposes)
under a power conferred by this Division, but only if authorised by the roads
authority in accordance with this section.
(2) The authority--
(a) must be in
writing, and
(b) must be given in respect of the particular entry concerned,
and
(c) must specify the circumstances which are required to exist before
force may be used.