There were about six photographers there last evening, all of us waiting for what started as a pretty hazy and grey sunset to turn into a feast of colors at dusk. The show was delivered on time, but the atmosphere was still a bit hazy, hence the non very sharp appearance of the distant buildings.
The green line you see across the frame is not a defect of the sensor. It's the laser beam that shoots out of the Observatory towards the other side of the Thames to mark the Greenwich Meridian line. Using a polarizer really helped in bringing out the color of the beam and of the sky above.