Chris D.
Yelp
I was lucky enough to have The Little One as my local coffee shop when we lived in Primrose Hill, and despite the plentiful competition from places that will make you coffee up and down the high street, they invariably stood head & shoulders above the rest. It's a tiny little place, but the staff are always enthusiastic and eager to help, and the Monmouth coffee is made quickly but expertly.
There are also fresh muffins (the blueberry was my weakness, though the chocolate & coconut was another favorite) and various Brazilian savory snacks; if you're lucky, you might get there on a "bacon sandwich day" when they make fresh breakfasts, too. It's a popular place for people working in the nearby shops and offices, and I'm not surprised.