With the news that Britain's counterintelligence agency, MI5, is looking for a chief scientific adviser, spy novelist Jeremy Duns reveals his 10 favorite real espionage inventions.

1. Poison-tipped umbrella

Probably the most infamous real-life spy gadget is the umbrella used by the Bulgarian secret services — with KGB help — to kill dissident writer and broadcaster Georgi Markov. KGB technicians converted the tip of an ordinary umbrella into a silenced gun that could fire a pellet containing a lethal dose of ricin, a deadly poison. On Sept. 7, 1978, Markov felt himself being jabbed in the thigh as he walked across Waterloo Bridge. A man behind him apologized and stepped into a taxi. Markov died four days later. No arrests have ever been made.

2. Dart gun

It wasn't just Soviet bloc spies who used such techniques, though. In a 1975 U.S. Senate hearing on intelligence, CIA director William Colby handed the committee's chairman a gun developed by his researchers.

Equipped with a telescopic sight, it could accurately fire a tiny dart — tipped with shellfish toxin or cobra venom — up to 250 feet. Colby claimed that, as far as he knew, this and other weapons had never been used, but he couldn't entirely rule out the possibility.

3. Compass buttons

During the war, the Special Operations Executive — "Churchill's secret army" — created a wealth of James Bond-like devices. One ingenious invention was magnetized trouser buttons, which were to be used for agent who became lost — if they were taken prisoner, for example. By cutting off the buttons and balancing them on each other, they turned into compasses.

• Click here to find out the rest of the top 10 in the Times of London.

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