I drove to my parents last night. As I was driving round the Tulse Hill one way system something suddenly turned on siren. This was a bit unsettling, as I was heading towards a crossroads at about 25mph with the lights green in my favour, and had no idea whether something was now about to cross it and potentially hit me. About half a second later I located the siren. It was on a police van proceding the wrong way round the one way system, about to go against the lights in conflict with me. W.T.F. was it doing approaching the lights with its sirens off, only turning them on when it got close? The only thing to their credit was that they were proceding cautiously (about 10-15mph), so weren't likely to collide with anything. But it doesn't inspire me with confidence.