From the shape & condition of this tree as well as its likely age - it
looks like it's been 'rescued' several times before. It's badly
misshapen, is rotting in more than 1 places, is not a good fruiter &
would need to be savagely cut back to even last another few years.
I've been told by the tree surgeon & also an experienced professional
gardener that it's on it's way out.

Frankly - it's a pretty sorry thing and while it might be technically
possible to prolong its life by another couple of years, to be honest
in my books it's time has come, so any advice on replacement would be
welcome.

Regards,

Michael