I was in London last November with my two daughters. I had a two hour window of free-time and had to choose between American Classics or Son of Stag. I went with Son of Stag . . . great store! I will visit American Classics and the new RMC store on my next visit.
I prefer Rivet and Hide to Son of a Stag.
With a two hour window, I'd have started with Rivet and Hide, walked down to American Classics, and then onto RMC and the Cabourn stores. The last two are pretty much on opposite sides of the street.