On 3 November 2006, Litvinenko (under the name of Edwin Carter) was admitted for further investigation at Barnet Hospital, London. After being moved from his local hospital in north London to University College Hospital in central London for intensive care, his blood and urine samples were sent to the UK's Atomic Weapons Establishment (AWE) for testing. Scientists at AWE tested for radioactive poison using gamma spectroscopy. No discernible gamma rays were initially detected; however, a small gamma ray spike was noticed at an energy of 803 kilo-electron volts (keV), barely visible above the background. The BBC reported that by coincidence another scientist, who had worked on Britain's early atomic bomb programme decades before, happened to overhear a discussion about the small spike and recognized it as the gamma ray signal from the radioactive decay of polonium-210, which was a critical component of early nuclear bombs. On the evening of 22 November, shortly before his death, his doctors were informed the poison was likely to be polonium-210. Further tests on a larger urine sample using spectroscopy designed to detect alpha particles confirmed the result the following day.