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This term is used to describe a Lease which comes into possession in the future. Unlike a Freehold which is only recognized by law when it is In possession (see fee simple absolute in possession), a legal lease can take effect up to 21 years after grant.

Annoyingly, a 'reversionary lease' is not in any sense the same as a 'lease of the reversion', which is another term for a ConcurrentLease oroverriding lease.