Alexander Litvinenko was poisoned by polonium in a cup of tea in 2006

A radiation expert who helped investigate the poisoning of Alexander Litvinenko was found dead five months after a trip to Russia, an inquest heard.

Matthew Puncher, 46, bled to death at his home after stabbing himself multiple times.

A pathologist said that he could not “entirely exclude” the possibility that someone else was involved in the death in May but concluded the injuries were self-inflicted. Now a coroner in Oxford has ruled that Dr Puncher took his own life.

Dr Puncher, an expert in the absorption of radiation, discovered the amount of polonium inside Mr Litvinenko, the former Russian spy, after he was poisoned by a cup of tea in 2006.

He worked for Public Health England at the Atomic Energy Research Establishment near Harwell,