Planning!

Well, a nice man at the Council Planning Department has told me the process.

Yes, you need permission.

Yes, it is a sensitive area with its own area authority that will need to oversee the idea first.

Yes, Parks and Amenities will also have to have a view of the ideas too.

So what to do?

Contact all those people, submitting drawings, views, etc.
Receive feedback from Parks, and from the E & C local group.
Consult Southwark pre-planning advisory group. They promise to reply within 21 days, three weeks just for that!
Review plans in the light of the feedback.
Submit for planning approval, or disapproval, with a cheque for £135 perhaps, but possibly £265 as it not a domestic, residential submission. They promise to reply within eight weeks.
In the light of the permissions received and the feedback, begin installation.

Count the weeks!

My best man was/is a townplanner, thank goodness I was able to give him many months notice of the event!

Alternatively, "Go guerrilla.."

and risk the wrath of the Community Wardens whose job description is available from the Council.

What to do? ( Bit of an in joke there, sorry readers.)