In the UK, a "pony" is a slang term for which sum of money?

The slang term "pony" is used to refer to £25. While there are a few different theories about the origin of this term, one of the most commonly cited explanations is related to the idea of a "pony express." In the 19th century, the Pony Express was a mail delivery service in the United States that used horses to transport mail across long distances. The service was known for its speed and efficiency, and it quickly became a symbol of reliability and trustworthiness. Over time, the term "pony" became associated with the idea of something that was reliable and trustworthy, and it began to be used as slang for money.

One theory is that the term "pony" specifically came to be associated with £25 because it was the cost of a pony at the time. This meant that if someone wanted to purchase a pony, they would need to have £25 on hand. Over time, the term "pony" began to be used more broadly to refer to any amount of money, as long as it was a relatively small sum. It may also originate from the Latin words "legem pone", which means, 'payment of money'.

Like many slang terms, the origin of "pony" is somewhat murky and difficult to pin down. There are other theories that suggest the term may have come from the idea of a small horse (which is what a pony is), or from a different cultural reference altogether. Regardless of its origin, however, the term "pony" has persisted over time and remains a popular slang term for £25 to this day.