Marriage Value / Marriage Fee
When you extend a lease that has less than 80 years to run, there is an additional fee to be paid to the landlord called a Marriage Fee. When a Lease is extended, it adds value to the property, sometimes this can be a substantial amount. Under the 1993 Leasehold Reform Act, the landlord is entitled to half of the increase in the value of the property when a <80 year lease is extended, this is called the Marriage value or Marriage fee, so-called because the value of the property + longer Lease (i.e. when Married together) exceed the combined value of the separate entities. When you extend a lease with a remaining term of 80 years or more, no marriage fee is payable. You should always look to extend a lease before it hits the 80 year mark for this reason.

The payment by the leaseholder to the freeholder when the lease is extended (or Enfranchised) is the Premium.

When you buy a leasehold property, the lease is Assigned to you.

A lease is enfranchised when the leaseholder (house) or leaseholders (block of flats) acquire / buy the freehold and take full ownership of the property, this has the effect of ending the lease.

If the leaseholder breaches the terms of the lease (the breach must be significant) a Court can terminate or Forfeit the lease prematurely and return the property to the freeholder. Forfeiture is the ultimate sanction available to the landlord and requires a Court Order.

A lease is determined when it comes to an end for a positive reason, e.g. the freeholder buys the lease back from the leaseholder.

When a lease comes to a natural end, e.g. after 99/125 years, ownership of the property reverts back to the landlord.

Leasehold Valuation Tribunal (LVT)
Effectively an informal 'Property Court' designed to settle disputes between leaseholders and freeholders. An LVT consists of a panel of three; a solicitor, a surveyor and a layman. An example of when an LVT might be used is if you extend your lease but can't agree the Premium (fee) with the landlord; you would then refer the matter to your local LVT and they will set the Premium payable for the extension, you may appeal, but ultimately the LVT decision is binding on both sides.