The charge taking effect by virtue of section 11B (charge for repayment of discount) has priority immediately after any legal charge securing an amount—
subject to the following provisions.
The registered social landlord may at any time by notice served on an approved lending institution postpone the charge taking effect by virtue of section 11B to an advance or further advance which—
and the landlord shall serve such a notice if the purpose of the advance or further advance is an approved purpose.
In this section "approved lending institution" means—
Where different parts of an advance or further advance are made for different purposes, each of those parts shall be regarded as a separate advance or further advance for the purposes of this section.