Love this place, and have for years. It's tucked out of the way of any traffic, but is just a stone's throw from St. James St, and then a few blocks to Jermyn Street or Piccadilly. Fantastic restaurant downstairs, and the bar may actually be as good as its reputation. I wouldn't know the full answer to that, as I've never been able to get in. I did have a few drinks brought to the salon next door, however, and the G&T was especially fine, even to this non-G&T drinker.
The downside? It's obviously of a certain period, which might be a problem for some people. Personally I don't mind, even though the layout is a little convoluted and the rooms are on the small side. The latter is what keeps the prices reasonable, and I don't need any more than they offer in that department.