So after visiting Manor Park in London, which is a private cemetery managed by it's original owners, I decided to give them a call and make some enquiries.
A very helpful lady informed me that the large sunken sight I had photographed, was infact a public ~ paupers ~ grave.
All privately owned plots have a timed lease ~ 50 or 75 years ~ which maybe extended if wished.
When the lease expires the owners are informed and if no further instruction is given, the gravestones are removed and the remains stay in situ. The plot may then be re-used later.
The headstones and vases below come from a public grave plot whose time was up....