Section 857 | Position where lease may be varied
From legislation.gov.uk
(1)This section applies if under the new lease L, or a person linked to L, has power to vary, in a manner beneficial to L or a person linked to L, obligations under the lease that are obligations of L or a person linked to L.
(2)The term of the lease must be treated as ending on the earliest date with effect from which L, or a person linked to L, could vary the obligations by exercising the power.