The name’s Bond. James Bond,” declares a suave Sean Connery, looking up from the roulette table in Dr No. The scene, part of a montage of defining moments from several Bond films, forms an introduction to Secret War, a new and permanent exhibition at the Imperial War Museum, London. The monitors showing the clips sit among toys, games and books, most of which mirror the excitement and glamour of the Bond movies. The real thing, as visitors soon discover, is a far more deadly, not to say dirty, affair.

In sections labelled MI5, MI6, Secret Communications, The Special Operations Executive (SOE) and The Secret Soldiers, hundreds of individual exhibits give some idea of the often brutal history of British clandestine operations. Here are weapons, maps, films, medals, photographs and gadgets that tell tales of heroism, cowardice, ingenuity, duplicity and danger by the dozen.

Central to one such story is the courageous Oluf Reed-Olsen, a Norwegian MI6 agent during the Second World War. On show are Reed-Olsen’s false identity card, various photographs and his Mauser pistol - “which helped to save his life on three occasions”, we are cryptically informed. Happily, Olsen lived to tell the tale. Not so some of the Czech agents whose names are listed in a notebook that forms part of a different display. The agents, all young students, were killed by the Nazis after the 1942 assassination of SS Obergruppenfuehrer Reinhard Heydrich, the notorious “Butcher of Prague”.

Less sensational, but of undoubtedly greater military importance, was the top secret intelligence work devoted to cracking the German military code transmitted through the dauntingly complex Enigma machine, one of which has its own display case. Alongside, an interactive video outlines the part played by the decryption process in the 1943 tracking and eventual sinking of the German battleship Scharnhorst, along with all but 36 of the ship’s complement of 2,000 men.

From all the surveillance devices, deadly weapons and espionage gear, both crude - invisible ink, for instance - and sophisticated - night vision goggles and the like - it is the more individual mementoes that are the most telling: a bloodstained attache case, souvenir of a narrow escape; the identity card of a captured British wireless officer soon to die in Buchenwald concentration camp; and a steward’s pass for the 1939 Earl’s Court rally of the British Union of Fascists, a body then sufficiently influential to merit infiltration by MI5. Small items, but with a significance altogether disproportionate to their size.

But for those who prefer the bigger picture, there are other attractions, in particular two splendid, multi-media displays towards the end of the exhibition. The first, a re-creation of the Second World War SAS raid on a German garrison in Benina, Libya, is pure Boys’ Own: a series of comic-book illustrations punctuated by explosions, stirring music and gung-ho sentiments. And, at the last, an equally vivid recall of Operation Nimrod, the violent resolution of the 1980 Iranian embassy hostage crisis - a finale which 007 himself would have applauded.

* Secret War at The Imperial War Museum, Lambeth Road, London SE1 6HZ. Booking essential: 0171 416 5313.