A local housing authority may by agreement with a person having therequisite interest execute at his expense—
any works towards the cost of which a grant under this Part is payable ormight be paid on an application duly made and approved; and
any further works which it is in their opinion necessary or desirable toexecute together with the works mentioned in paragraph (a) above.
Except in the case of a common parts grant, the "requisite interest" means an owner's interest in everyparcel of land on which the works are to be carried out or, in a case where(if an application was made) section 104(4) above might apply, in part onlyof the land concerned.
In the case of a common parts grant, the reference in subsection (1) aboveto a person having the requisite interest is a reference to the personwho—
has a power or duty to carry out the relevant works; and
has such an interest in the building or in a flat in the building as isreferred to in subsection (4) of section 105 above.