When Herzog and de Meuron designed Tate Modern's new Switch House extension, they didn't consider that visitors would be unable to resist the temptation to walk along the narrow perimiter wall.
The southern entrance to the new is enclosed by a walk that follows the shape of the former oil tanks of Bankside Power Station which lie underneath.
Tate has installed security fencing around the lower parts of the wall after the wall proved an irressistible challenge to some visitors.
Responding to a question posed by the SE1 website, Tate director Sir Nicholas Serota said this week: "Clearly some of our visitors are more intrepid than perhaps our architects had appreciated, and we are about to put on top of that wall a small balustrade that will make it more difficult to climb on and walk along, at which point those unsightly fences will come down."
This week Tate has been embroiled in a controversy over complaints from residents in the adjacent Neo Bankside luxury flats about gallery visitors looking into their homes from the 10th floor public viewing gallery.