I stayed at The Wellesley in July 2014 for two nights and, based on that experience, was wowed. On check-in, my wife and I were asked if we would like to upgrade to a suite for a nominal fee. We accepted, and in doing so, transformed our experience.
The staff: we arrived fairly early from Dublin (where we had stayed the previous several days) and were rushing to Nottinham for a family event. The staff was very accommodating, allowing us early check-in to our room and giving us the option of morning tea (though we were not told that we would be charged for the tea). Our butler was amazing; on our return from Nottingham late that night, our luggage was unpacked and neatly placed on the shelves (I was just glad that my dirty laundry was in a separate, clearly identified area). She was also instrumental in getting our formal clothes ready in record time - this more than helped us to overlook the tea incident. As an icing to an incredible staff experience, we were also given a courtesy ride to Novikov (to have dinner with friends) in The Wellesley's Rolls-Royce house car - I beamed.
The room: we were given the Ella Fitzgerald suite (so I am unable to comment on the standard room). The room was amazing, and I was almost overwhelmed by the attention to detail and luxury that it exuded. The bathroom presentation was exquisite (Hermes toiletries and heated flooring helps in this regard) and the bed was fairly comfortable.
I wish we had more time to spend at the Wellesley, but home beckoned and we had to bid adieu. It will remain one of my top choices for hotels in London for my next visit.