Well stocked tobacconist in London city?

My brother and his wife are leaving for London in one week and I’m sending him with a shopping list for snuff and he will be hunting for Cubans (the cigars, not the people) since the blasted embargo against Cuba laid by JFK is still in effect, for some Godforsaken reason.  Can anyone recommend a good purveyor with a wide assortment of tobacco in the city?  No, I don’t know where in London they are staying but I’m certain that if it’s worth it he’ll take the tube wherever he needs to.  Thanks in advance!!