Heritable Interest: The outright ownership of property as opposed to
a leasehold interest. The English equivalent of Freehold.

http://www.gva.co.uk/valuation/our-guide-to-valuation-termin...

Freehold vs. Leasehold:

Leasehold: Method of owning property (usually a flat) for a fixed term but not the land on which it stands. Possession of the property will be subject to the payment of an annual ground rent. When the lease expires, ownership of the property reverts back to the freeholder. Nearly all flats in London are leasehold.

Freehold: Outright ownership of the property and land on which it stands. A freehold estate in land (as opposed to a leasehold) is where the owner of the land has no time limit to his period of ownership.

http://www.ludlowthompson.com/property_advice/Whats_the_diff...