How times change. Relations between Britain and Germany are better than for many years. Angela Merkel met the Queen and addressed both houses of Parliament this week, safe in the knowledge that her approval rating in the UK is higher than anywhere else in the EU.

Yet 70 years ago a network of German spies - the Abwehr -were doing their utmost to bring the UK to its knees. Britain's intelligence agency MI5 has just published details about some of the most infamous agents; and how they were tricked, coerced or persuaded into betraying the "Fatherland".

At the beginning of the second world war, MI5 was overwhelmed by the amount of information it received and had to try and process. This information included details of shadowy figures across Europe, mainly in neutral countries like Portugal and Spain, who were suspected of spying for Germany.

Among their number were Baroness Marie Von Granau, who slept with spies and military officers from Britain, Italy and Germany; Georg Hansen, deputy chief of Germany's intelligence service who joined a plot to assassinate Hitler and was hanged; and Admiral Wilhelm Canaris, who was executed for high treason after apparently making "overtures" to the Allies.

Almost all the German spies were either tricked or turned, and many of them went on to supply the UK with important information – as well as feeding misinformation to the Nazis. This culminated in one of the most successful spying operations of all time, Operation Garbo, when double agent Juan Pujol deceived the Germans and helped ensure the success of the D-Day landings.

The newly-released files illustrate the deep concern felt over suspected fascist sympathisers within the UK, who it was believed might help prepare the way for a German invasion. Sir Oswald Mosley, Nazi sympathiser and leader of the British Union of Fascists, was arrested in 1940 over his links with Nazi Germany.

The files also reveal that Shakespearean actor Sir Michael Redgrave was monitored for years due to his socialist sympathies; and that the extreme Zionist group the Stern Gang plotted to assassinate Winston Churchill.

Yet the files are also an important social document, in whose pages can be found a genuine flavour of what it was like to live in London in the middle of a war which almost led to the destruction of the country as we know it; a time of terror, paranoia and astonishing bravery.