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The British Special Operations Executive (SOE) came up with all kinds of bizarre ideas but perhaps none more so than the ‘exploding rat’. Developed in 1941, the aim was to blow up the enemy’s boilers by lying the rat – a taxidermied rodent with a detonator inside – on the coal beside the boiler. The fuse would supposedly be lit when the rat was shovelled into the fire.

The source of the dead rats was a London supplier, under the mistaken belief his client was London University (100 were acquired by an SOE officer posing as a student needing them for laboratory experiments).

The first consignment was seized by the enemy. The Germans were fascinated by the idea, however, and the rats were exhibited at top military schools. Indeed, SOE files show that they actually organised searches for these rodent explosives. Files released in 1999 stated: “The trouble caused to them was a much greater success to us than if the rats had actually been used.”

A white rat, with an unused pencil detonator inserted inside, was estimated at £300-500 at East Bristol Auctions (18% buyer’s premium) on November 20. Presumed to be a practice/exhibit example, it sold for £850.

A more ‘conventional’ device sold at £1800 (estimate £250-400) was a set of three Second World War ‘escape dominoes’ with secret maps hidden within each one. The ‘ivory’ domino tops are card and each removes to reveal small sections of maps of Europe and Burma.

Both lots mentioned went to an American private collector.

These were just two out of an extensive collection of such gadgets formed by the late Arthur Muggeridge (1919-2010). Following his own military adventures, which included injuries sustained at Dunkirk and in Norway while involved in a 1941 raid called Operation Claymore, in later life he collected military items and particularly spy objects. When visiting Devon in the 1960s Muggeridge became acquainted with Charles Frazer Smith, who had worked for MI6 and MI9 in the war and designed spy items for the SOE and others.

Muggeridge’s collection is being offered for sale by his family. East Bristol offered a first selection in May this year.

Compasses pointed out at auction

On November 20, Derbyshire saleroom Hansons (25% buyer’s premium) sold a large private collection of Second World War spy gadgets amassed over 40 years.

Items such as these were produced by MI9, a department of the war office between 1939-45, and were given to SOE agents.

Compasses were essential tools for agents parachuted into enemy territory or for Allied air crew trying to escape and were concealed in all manner of everyday items from pencils to collar studs and buttons.

Hansons sold a full set of battledress compass buttons, some 25 mint examples that were unissued on card in and in an original stores cardboard box for a top-estimate £1000.

Sold at £1000, against an estimate of £500-800, was an RAF/SOE pipe with hidden escape compass in the stem. The maker was marked Dagon.

Another particularly ingenious design was an RAF pencil clip compass. This could be balanced on a pencil point by placing it into the impressed dimple, allowing the magnetised clip to swing and act as a compass. One of several examples at Hansons made £420 against a guide of £40-60.

All three lots mentioned went to UK buyers.

Secret codes on silk

Coming up at Tennants’ Militaria and Ethnographica auction on December 16 is a Second World War cryptology silk square, printed with a list of French codes.

It belonged to Joyce Mary Pimblott, who was a cypher officer for the SOE handling communications with the French Resistance and British secret agents operating in France.

She was born in Lancashire but moved with her family to Brussels when she was young and grew up speaking French. At the outbreak of the war the family returned to England. Pimblott lied about her age (she was only 17) and joined the First Aid Nursing Yeomanry.

After her initial training, and on the discovery that she spoke fluent French, she was transferred to the SOE where she embarked on her secret wartime career. She played a key role in communications surrounding the D-Day landing and later translated documents required for the Nuremburg Trials.

Silk was a durable and practical medium for printing codes: it was lightweight and unlike paper would not disintegrate or run if wet, and it could also be sewn into the lining of clothes without detection.

Estimate: £400-600.