Why things are the way they are
It can be be traced to reforms instituted by Charlemagne in the 9th century. Those changes stated that 240 silver pennies should be minted out of a pound of pure silver. Twelve of the pennies would be called a shilling. The pound was a unit of weight out of which 240 pennies would be minted from, although gradually it reduced in value to about one half of its original silver content by the end of the 15th century, and to about one third by 1601. Silver was not devalued anymore until gold replaced silver after 1696, although the governing laws came in much later .
The Metric System
In 1791 the National Assembly in France approached the Academy of Sciences to investigate the problem of chaotic weights and measures then in use, and from there invent an improved system. The scientists decided to base the new mechanism on a natural unit that could not vary (in their view). It was decided to use one-ten-millionth of the meridian that passes through Paris from the North Pole to the Equator. The value is equivalent of 39.37008 inches. The Greek word of meter, meaning measure was used for this unit.
Why the British drive on the left hand side of the road
When roads or tracks were first created, the highway was a much more dangerous place than it is today. What was important was that when meeting oncoming people you met them with your right or sword arm facing them, therefore you occupied the left hand side of the track. This meant if trouble happened you were perfectly positioned to response to the danger. Although this need has long since disappeared the tradition of being on the left hand side remains in the UK.