Why the Queen Elizabeth class began with five ships

Why was the Queen Elizabeth class ordered as five ships when battle squadrons used even numbers?

Orders were shaped by budget and timing; a sixth ship was added later, and the eight-ship squadron convention was already becoming less decisive.

Five Queen Elizabeths were initially ordered before a sixth was added, while the Revenge class was planned at eight. Treasury limits and the timing of parliamentary approvals could break a desired squadron into several orders. By the Second World War, capital ships were too scarce and widely deployed for the old eight-ship squadron model to govern every class. A five-ship order therefore reflects budget and transition rather than a belief that battle squadrons required an odd number.