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Cameron told Newsnight he wanted kids to learn Imperial measures. This is how he wants to the British workforce to calculate weights and distance.

This is how weird Imperial measurements are

You might think a pony is just a small horse, but it's also a measurement - 19 ml, in fact. That's 1.5 mouthfuls, another odd measurement that our ancestors used.

Those are just two of the old English measurements that have thankfully been replaced by the metric system.

One metre, measured in barleycorn and poppyseeds, would come to 118 barleycorn and half a poppyseed.

Of course, to measure your poppyseed by weight, you'd have to use grains. 100 grams comes out as 1543 grain, or three ounces and eight and a half drachms - not to be confused with a dram of whisky, which at 25 ml is the equivalent of seven fluidrams. Simple.

The football pitch at Old Trafford is approximately 7140m2. In old measures, it comes out at 1 acre, 3 roods and 2 perch. Rood is an Old English word for a cross or crucifix; a perch is a fish.

Many Imperial measures are based on body parts

The weirdness of the Imperial system doesn't help international business, particularly when the words can be mistranslated. Body-based measurements include feet, digits and, for a length of 6 inches, shaftements. Imagine explaining that one to a Chinese business partner.

Another old English measure for a meter would be 13 palms and half a finger.

By the way, a finger is 2.2225 cm. An actual finger is usually three times that long. So your finger could measure three fingers.

That's not to be confused with digits, which are based on the width of a human finger and come out as 7/6 of a finger. Naturally.

Then there's hands, the common measure for measuring the height of a horse, which is written in base four. If I were a filly, at 5ft3 (or 1.55m) I'd be 15 and three quarter hands, or 15.3 written down (base four, remember).

The volume of an Olympic swimming pool is usually written metrically as 2500m3 but under Imperial measurements it's also 8,593 hogsheads, one comb and a strike or, alternatively, 2.1 billion fluid scruples.

Got that? Good. Because, if the Tories have their way, there's going to be an exam.