14 August 1803: As Napoleon wages war across Europe the Observer reports on the arrests of ‘suspicious persons’ across the UK.
23 April 1855: During the Crimean war a Russian woman is apprehended outside Sebastopol. ‘Her note-book was found to contain several details relative to the situation of our batteries, and the number of guns...she had also in her pockets a double barrelled pistol.’
2 November 1898: In a case of mistaken identity, ex-civil servant Mr J.J. Etherington of Ipswich, is arrested as a supposed Russian spy.
15 January 1914: The Manchester Guardian runs an editorial expressing concern that the Russian secret police act with impunity in London.
4 April 1914: As tensions mount between the European powers a German spy caught recording British naval secrets is sentenced to six years imprisonment.
30 October 1915: The Manchester Guardian reports on the memorial service held for Edith Cavell at St Paul’s. The British nurse was executed by the Germans on a charge of harbouring fugitive troops and aiding their escape.
14 January 1939: Captain Franz von Rintelen, chief of the German Secret Service in the US during the first world war, is the guest of the Manchester Publicity Club.
16 June 1953: Julius and Ethel Rosenberg, accused of handing over atomic secrets to the USSR, are offered a glimmer of hope when Justice William Douglas agrees to consider a stay of execution.
29 November 1954: Alistair Cooke reports from America on the release of suspected communist spy Alger Hiss.
2 July 1963: Kim Philby is identified as the third man in the Cambridge spy ring.
25 September 1971: Britain expels 90 Soviet diplomats accused of planning acts of sabotage.
17 November 1979: Following Anthony Blunt’s exposure as the fourth man in Cambridge, the Guardian asks why the establishment allowed him ‘to lead an unsullied, honoured life at court - not reproved but regally blessed?’
19 April 2013: Guardian readers choose their top 10 spies.
28 September 2016: As MI5 files are moved to the National Archives, declassified documents reveal how a double agent’s homesick wife nearly put D-day preparations at risk.