Of all the memorable phrases that have been minted and mobilised to describe modern British royalty, 'constitutional monarchy' is virtually the only one which seemes to have neither been anticipated nor invented by Walter Bagehot. It was he who insisted that 'a princely marriage is the brilliant edition of a universal fact, and as such it rivets mankind'; and he who warned that the monarchy's 'mystery is its life. We must not let in daylight upon magic'.