With Britain announcing Wednesday the expulsion of 23 diplomats in response to a nerve agent attack against a Russian former double agent in England earlier this month, here are previous sanctions by London on Moscow in spying affairs.

- Expulsions of Soviet diplomats -

- In September 1971 Britain expelled a record number of 105 Soviet diplomats and officials, after Moscow refused to clarify the activities of 440 of its citizens in Britain.

Moscow in turn expelled 18 Britons.

- In September 1985 Moscow and London engaged in a furious six-day exchange of spy expulsions, declaring a draw after 31 on each side had been sent packing. This followed the defection to Britain of the KGB's London station chief, Oleg Gordievsky.

- In May 1989, 11 Soviet diplomats and journalists were thrown out for spying. Meanwhile 11 Britons were sent home from Moscow in a tit-for-tat move.

- Expulsions of Russians -

- In May 1996 Britain ordered the expulsion of four Russians working at the London embassy, in response to the kicking out of four British diplomats from Russia.

According to Moscow, the Britons were in contact with a Russian working for British intelligence.

- In July 2007 Britain expelled four Russian diplomats and hit Moscow with visa restrictions after Moscow refused to extradite Andrei Lugovoi, the main suspect in the murder of ex-Russian agent Alexander Litvinenko.

Litvinenko was poisoned in London in 2006 with the radioactive substance polonium-210, in the most notorious of a rash of suspicious deaths of high-profile Russian exiles in Britain.

Moscow responded with the expulsion of four British diplomats, suspended counter-terrorism cooperation with London and also stopped issuing visas to British officials.

In January 2016, after a British probe found that Moscow was responsible for the affair, the British government summoned Russia's ambassador, and froze the assets of Lugovoi and a second suspect, Dmitry Kovtun.