This is very easy to overlook, and even more so since the identifying plaque was first damaged and then completely removed. It's a small sapling, staked up near to the former bowls pavilion on the northern side.
The plaque looked like this:
The text reads:
This Royal Elm
was planted by
Lord Lieutenant Mr Peter Field
on 16th March 2012
in celebration of the
Queens Diamond Jubilee
Organised by Rotary Clubs
of the City of Brighton & Hove
All that now remains is the wooden backing of the plaque. I first noticed that all that remained was the bottom right hand corner; and a few weeks later not even that was left. Should it be replaced, I hope that the punctuation will be corrected!