Mercury Gardens is the site of the former Mercury Training Establishment which moved to the River Hamble in 1892 and established a shore based school along with the Training Ship.

The school closed in July 1968 and eventually made way for the present housing estate. All that remains is the mercury memorial plinth which can be found on the site.

More information can be found here...

link

There is also an excellent website by Richard Briggs which gives more detail of the history of the TS Mercury. Richard was given a camera by his parents in 1966 and having no other outlet for which to use his camera, Richard (though he did not know it at the time), would record and document for posterity the final years of the Mercury establishment.

See Richard's site here