THE TOXINS LINKED TO RUSSIA

CURARE

Under Joseph Stalin, Soviet scientists used curare, a plant extract first used in poison arrows by South American tribes.

American-born Communist spy Isaiah Oggins was executed in 1947 using this drug, which causes the respiratory muscles to contract and asphyxiates the victim.

RICIN

Cold War dissident Georgi Markov was assassinated on the streets of London in 1978 by a Bulgarian secret service agent, who used an umbrella which fired a pellet of ricin into his leg.

POLONIUM-210

The radioactive substance was used to kill former Russian spy Alexander Litvinenko in London in 200 . It was slipped into a cup of green tea at the Millennium Hotel in Mayfair.

The toxin is considered an ideal poison because it is harmless until swallowed – and then just a minuscule amount will cause a slow, painful death. It is almost impossible to acquire without a nuclear reactor and decays within a few months.

TCDD

This type of dioxin, an ingredient of Agent Orange, was used in the attempted assassination of Ukrainian opposition leader Viktor Yushchenko in 2004. He survived the attack and became his country’s president – but has major facial disfigurements.

GELSEMIUM

Russian businessman Alexander Perepilichnyy is believed to have been poisoned with a rare plant poison slipped into his sorrel soup.

Police first thought his death was not suspicious because there were no signs of toxins after he died in Surrey in 2012. But scientists later discovered chemical traces of gelsemium – an extremely poisonous plant – in his stomach. An inquest into his death has been adjourned pending further inquiries.