Potassium

There are two Knights we can link to Nottingham.

John Peake Knight (13 December 1828 – 23 July 1886) was an English railway engineer and inventor, credited with inventing the traffic light in 1868.

Knight was born in Nottingham and attended Nottingham High School. He left school at 12 to work in the parcel room of Derby railway station. Peake Knight was promoted quickly and by the age of 20 was Traffic Manager for the London to Brighton Line. He did a great deal to improve the quality of railway travel, introducing the Pullman car and safe carriages with alarm pulls.

In 1866, a year in which 1,102 people were killed and 1,334 injured on roads in London, Knight proposed a signalling system to regulate the horse-drawn traffic and reduce the number of road accidents.

Knight's invention was operated by a policeman and used a semaphore, system based on railway signalling, during the day and red and green gas-powered lamps at night. However, the gas lamp exploded and killed a policeman in 1869 resulting in the lights being removed.

It would be 40 years before traffic lights reappeared and this would be in America.

They would only become a common sight in London in 1929 when the first electric signals were introduced.

Of course, we can also link The Dark Knight Rises to the letter K. In 2011, key scenes from the Batman movie were filmed outside Wollaton Hall. The Hall was featured as the latest Wayne Manor. It is five miles north of Gotham, Nottinghamshire, through which Gotham City indirectly got its name.

Potassium is the seventh most abundant element on Earth.

It was first isolated by Sir Humphry Davy in 1807.

Potassium was the first elemental metal to be found through electrolysis.