As dusk falls in London and the lights come on, the grammar of the city begins to break down. Humdrum office buildings compete to outshine each other, while monuments such as St Paul’s Cathedral recede into darkness. Public parks become inky voids, but bright security lighting lends a lively aura to inconsequential parking lots. A calm corrective to this high-wattage anarchy is being offered by a new light-based artwork by the American artist Leo Villareal with London architect Lifschutz Davidson Sandilands. Phase I of Illuminated River, as it’s called, has recently been installed on four Thames River bridges, and will eventually extend to 15 river crossings.