Possible Clues:

• Unrivalled noblewoman, about fifty
• Supreme, unlike the House of Lords?
• Unique, like an empty House of Lords?
• Don't gawp so much - it really is outstanding
• Unrivalled steeplechaser gets rid of cheat and puts things right
• Unrivalled, but lacking nobility?
• Sleepers somehow beyond compare
• Unrivalled lady about 50
• Incomparable description of the House of Lords at the end of the day?
• Unequalled, unrivalled