A London skyscraper dubbed the Walkie-Talkie has been blamed for reflecting light which melted parts of a car parked on a nearby street. What happened?

It's like starting a fire with a parabolic mirror.

"Fundamentally it's reflection. If a building creates enough of a curve with a series of flat windows, which act like mirrors, the reflections all converge at one point, focusing and concentrating the light," says Chris Shepherd, from the Institute of Physics.

The half-finished 37-storey "Walkie Talkie"- nicknamed such because of its tapering rectangular design - is indeed a curvy building. Its design, which has also been compared to a brimming pint glass, has come under controversy before.