I have checked out yesterday and have to say that this hotel will need to go through renovations immediately. It is in a sad state and it is astonishing they charge higher rates than its sister properties.
The front desk and housekeeping are not trained to work in a luxury collection property. However, the concierge and butlers are great. Greg from the concierge actually gave me 1 GBP so I can use the trollies at St. Pancras (as I was travelling to Paris). I will definitely return that and some extra in the future while travelling to London.
The breakfast was basic and nothing to write home about. They had a Orange juice maker machine that was fun to use but broke down mid stay.
The views here are fantastic and we had a live view of British Summer Time music festival. You could listen to Adele as if you were playing music in your room.
All in all, I would go for the Mayfair properties if staying in London next time (unless you struck a suite at the PT). But the views are unbeatable here.