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Edward Dean Butler has owned some amazing cars.
An ex-Louis Chiron Bugatti Type 51, ERA R1A, an ex-factory Maserati 8CTF, one of three Allard J2s that raced at Le Mans in 1953 and the MG TD he has owned since he was 16.
Next to the garages that house his cars is an automotive library and collection of magazines that is one of the largest in the world.
In it is a complete set of Classic & Sports Car, Autocar, Motor, Car & Driver, Hot Rod and hundreds more.

Butler has got the collecting bug bad.
Apart from the cars and his world-class motoring library, Butler has a collection of more than 2000 slide rules.
Surely this must be the largest in the world? “I’m not sure,” he replies. “The head of chip research at Intel has a huge collection.”
“The slide rule was invented in Britain in the 1700s for use by tax collectors,” explains Butler.

“The calculation to check the amount of beer in a barrel was very complicated, especially because the barrels differed in size and the liquids varied,” he continues.
“There was no such thing as an imperial gallon and each product had its own measurement.”
Slide rules don’t take up as much space as cars. Or books.
There are drawers and drawers of them in Butler’s study, some of them extremely rare.

Butler shows one that has four sliding elements and then another that has six. “There are only two of these known to exist,” he says.
Butler has slide rules used to calculate the weight of powder required in cannons aboard naval ships, slide rules for working out trajectories for artillery shells and gunshot on land, and slide rules for working out longitude at sea.
“Many people will be familiar with John Harrison and his marine chronometer that enabled sailors to calculate longitude,” says Butler, “but these early clocks were so expensive that even the Royal Navy couldn’t afford them, so an analogue solution was needed.”

Most of Butler’s early slide rules are made from wood, the majority manufactured in the heart of slide-rule production in the Southwark area of south London.
A few early ones are in white ivory.
“James Watt, the inventor, thought it was crazy to have so many different slide rules, so he designed one that could be used to solve multiple problems,” explains Butler.
“The ones I’ve got might not have been used by Watt himself, but probably came from his workshops.”

Not surprisingly, the slide-rule industry disappeared overnight with the invention of the electronic calculator. Here we see some dangerous hobby creep, because Butler also appears to have a respectable collection of those.
“That one,” he says, pointing to a rather basic-looking machine, “was the first commercially available Texas Instruments calculator.”
Another is a calculator used by Soyuz astronauts in the late 1970s and early ’80s.
No Enigma machine? “I’d like one,” admits Butler, “but I’m not sure that the lady of the house will tolerate me spearing off in yet another direction.”

So why this obsession with scientific instruments, and slide rules in particular? “I’ve always been fascinated by engineering and by its evolution,” says Butler.
“Of all the cars I’ve owned, the Bugatti is my favourite because I find Ettore Bugatti and his approach to engineering and his commitment to high standards totally absorbing.
“I think there’s a direct link from the highly intelligent mathematicians and engineers, such as James Watt, who created many of these instruments and used them in practice, to 20th-century pioneers such as Bugatti.”
Images: Luc Lacey
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Also in my garage: Simon Taylor’s classic car magazines