In the initial days of various parks there are stories of a jar or two of uncracked pepper being sent to the head of the family that granted the land, this was somewhat in light hearted humour and also more or less took care of the rent for a few hundred years into the future.
These days there may well be the odd case in which a centenary celebration for a park might well invite a descendent of the family that bestowed a park and "formally" give them a peppergrinder, I can't think of many off hand.
At some point it may be the case that (say) Hyde Park in Perth, Western Australia becomes delinquent in rent and the descendants of the <redacted> family step up and form a class action demanding the return of the Park to themselves by the City of Vincent (or whomever holds the deed at that point).
The City could settle by simply throwing them a sack of peppercorns to squabble over amongst themselves.
The spirit of the lease is a "forever rental" for a sum of something trivial of actual value ( tea, spice, pepper, etc. once were more valuable in English society ) to make it binding but trivial to pay.
The more interesting case would be if a council did something with the land or a portion of the land that was deemed outside the terms of usage ( a private residence for the mayor rather than a groundskeeper's flat, perhaps ) - if public access wasn't restored then there would be a case to claim back half a billion dollars worth of real estate.
That would be the makings of an epic legal shitstorm and drama.