If a purchaser or his successor in title enters into an agreement within subsection (3), any liability arising under the covenant required by section 35 shall be determined as if a relevant disposal which is not an exempted disposal had occurred at the appropriate time.
In subsection (1) "the appropriate time" means—
An agreement is within this subsection if it is an agreement between the purchaser or his successor in title and any other person—
Such an agreement is within subsection (3)—
The Secretary of State may by order provide—
An order under subsection (5)—
In this section—