We stayed at the Athenaeum last weekend for one night for a theater break.
The service is excellent, staff are warm and friendly, the whole hotel, bar, toilets, rooms, restaurant are impressively spotless and comfortable.
The price of course if very high, but this is Mayfair, so top be expected.
The room again as expected was small, but efficient and well laid out with a very nice view of Green Park opposite.
The Breakfast was excellent, huge buffet or a hot menu that caters for all tastes, I had the full English which was delicious.
So, to the flaw, noise!!!!
After a long day we retired to bed at approx 11pm, just getting to sleep when our 'neighbor' returned to their room too. From that point on we could hear 'everything'; going on in their room, I am not exaggerating but i could hear the male gargling in the bathroom (and worse) and also his 'wife' who was making a call on her mobile, she must have had it on hands free because i could hear the dial tone and ringing until it was answered. Very disappointing.
So, as in all hotels, not all rooms are the same but this one was not enjoyable for sound dampening issues, other rooms in the hotel I am sure are fine, so would ultimately recommend this hotel as an excellent place to stay when visiting London.