Lots of leaseholds now start at 999 years.

It’s a weird system. The previous and current governments have been looking to modernise it.

Interesting. Do the longer ones have some provision for increasing in line with inflation? AFAIK the 99 year leases are usually for a fixed amount every year, which obviously shrinks in real terms over time, but given that you'd want to renew it every 10 years or so anyway, would probably be renegotiated to a fair market rate at that time.