Possible Clues:

• As was Prince George, say, gatecrashing opening
• Person appointed to rule when a monarch is a minor
• Someone ruling on behalf of another
• He takes charge temporarily, for example, during gap
• Substitute ruler
• One ruling on behalf of another
• Ruling about well-bred chap
• One ruling about a lady's man
• Return of Queen with fellow Prince?
• One acting on behalf of an incapacitated monarch