Situation : In a very pleasant location, very calm, not far from all busy sites too and Harrods ! Shopping obliged.
Very comfortable room with high quality set up (bed, bathroom, sofas and decoration), except towels too small.
Efficient, discreet and charming staff.
We didn't get the pleasure to have dinner in the place, because the restaurant was closed. But the breakfast is delicious and very quickly served by the room service.
I would like to say that the bar is not enough friendly, too cold and not enough cosy. But it's a detail.
However, it is a very comfortable hotel to recommend for a stay in London.

Pros
Modern facility with large rooms
Friendly staff
Excellent location
Quiet rooms and neighbourhood but easy access to many sites in London
Cons
Quite expensive
Windows are sealed however you can ask the staff to get them open

we decided to have a city break in london.the halkin is so well situated and we were totally happy we the whole setup of the hotel. staff were charming and efficent and our room was beautifuuly appointed and comfortable.only drawback-dinner at resraurant not up to expectation---breakfast was superb

We had a very nice stay at the Halkin. Room was nicely decorated, with everything you could need, and a nice bathroom with large bath and very powerful shower. Very comfortable bed.

Staff were friendly and a complimentary bottle of bubbly as it was my wife's birthday was a nice touch.

We also had afternoon tea, which was very nice and they accommodated my wfie's gluten allergy.

My only complaint is the price of the afternoon tea - £100 for 2, which included half a glass of champagne, was too much (3 half sandwiches, 6 mini scones and 2 cakes), I think this is not good value for money compared to other establishments, and the bar / restaurant are is lacking atmosphere.