I was up Spinnaker Tower in Portsmouth, using their fancy new tablet posts to find out the names of all the ships (like you do) when I glanced inland and saw this on top of part of Gunwharf, the floating shopping centre:
It's a little indistinct in the grey of the winter day, but distinctly a garden, next to a glasshouse, on top of luxury flats, on top of a shopping centre, like a wedding cake of endstate capitalism. Curious about whether it was public or private I zoomed in a little closer:
I spy with my little eye, a statue; a single large table; sad palms browned by winter rains; a double lounger; rough attempts at symmetrical placement interrupted by roof venting; and the classic mixture of semi-thrive and decline that characterises the absentee container gardener. I am guessing private; and that that glass-fronted half-floor it abuts onto is one fantastically huge penthouse suite flat. The mind boggles, but back to the garden.
It's a tough proposition, roof-gardening in the UK, and this garden says exactly why; wind-blasted, sprayed with brackish onshore rain laced with city particulate soup, and always fighting the fight between no light and far too exposed. Windbreaks cut out the sun, and turn into sails in storms. Containers get flooded and freeze or dry through and won't re-irrigate. Frost finds the rooftops first; the leaves brown and the roots wither or rot. The plants prefer more greenery around them, but the tonnage racks up fast, especially when the pots are soaked with winter rain.
Nevertheless, I'm currently (always) engaged in attempts to turn every flat garden roof I'm in contact with into a garden. The only way forward for our cities is to green every surface we can; and it's good to see this roof doing its bit.