Soz, meant to add this ... (from the link)
Robins can be easily triggered into full song by a streetlight or any kind of floodlighting. Since robins keep territories all year round, they also sing all round the year. This has resulted in dozens of reports of nightingales singing in the middle of the winters night and other equally unlikely times and places, which have all turned out to be robins. In fact, the robin is the most common night-time songster in Britain's towns and gardens.