Imagine you want to sell your car, but you’re simply too busy to deal with buyers. You ask a friend to handle the sale for you, and she shakes hands with a buyer and takes the cash. In law, your friend is acting as your agent, and you are the principal—the person who will be bound by the deal she makes. Agency is a very practical bit of English law. It comes up whenever one person acts on behalf of another. It shapes how businesses trade, how we instruct professionals, and how personal affairs are managed when we cannot act for ourselves.