MI5 delves into the history of spying in new London exhibition

(Corrects typo in the headline)

By Sam Tabahriti and Will Russell

LONDON (Reuters) -Britain's spy agency MI5 is revealing some secrets.

In collaboration with host The National Archives and prepared over several years by the agency's own archivists, "MI5: Official Secrets" is giving the public the chance to see equipment and methods used by the real life James Bond and his colleagues over the agency's 115-year history.

Ken McCallum, director general of MI5, said the agency wanted to be more transparent.

While TV fiction showed the dramatic side to spying, real intelligence work was about "ordinary human beings together doing extraordinary things", he said at an event on Tuesday launching the exhibition.

One of the featured items is a 110-year-old lemon, used as evidence against German spy Karl Muller, who was executed in 1915 at the Tower of London. Muller used lemon juice to write secret messages during World War One.

The display also includes confessions and surveillance reports relating to Britain's most notorious double agents, who spied for the Soviet Union between the 1930s and 1950s and were known as the "Cambridge Five".

"The reality of our work is often different from fiction - whether that fiction is George Smiley or Jackson Lamb," said McCallum.

Author John le Carré's George Smiley works for overseas intelligence agency MI6, dubbed "The Circus" by le Carré, while grumpy Jackson Lamb appears in TV show "Slow Horses," depicting a team of failed agents.

The exhibition opens on Saturday at The National Archives in southwest London and runs to September.

(Reporting by Sam Tabahriti and Will Russell, Editing by Rosalba O'Brien)