Caged and free

Cages of rocks like this, gabions, are used a lot along the edges of the Thames in Oxford to prevent erosion of the banks and provide stability for the tow path. They're a neat idea (an old idea - Leonardo da Vinci was onto it long ago). Elsewhere they're used in road-building and holding up precarious slopes. But these are about five metres back from the river at right angles to it, and placed in line with the staircase to a boathouse. I can't see what they're doing apart from providing blip-fodder on a day that's been too full for anything else.