There's been much hype about this little caff thanks to Time Out, Twitter and the much-welcomed trend among the capital's coffee connoisseurs to hunt down independent coffee shops.
Antipodean coffee, it seems, is enjoying something of a renaissance in London.
Flat White also does a mean breakfast, but first, the black stuff.
For starters, don't ask stupid questions about the coffee - as I did, because you're supposed to be a coffee pro if you're going get your caffeine hit from here.
I asked the difference between a cappuccino and the eponymous coffee that gave the establishment its name. "A flat white is stronger coffee and is superior, we just serve cappuccinos for ill-educated faux-epicureans like you, now bog off to Starbucks," was roughly the response I got from the harassed Aussie behind the counter.
In an attempt to win her over, I ordered a flat white with a piece of prune and walnut "cake" (above - it's flourless, egg-less and butter-less, so it is pretty much just softened prunes and walnut pieces). My mate had a macchiato.
Both were superb - nutty, rich coffee and thick, milk, foamy with fine bubbles and a pretty leaf pattern on top. The cake was tasty, but a little too virtuous to be called "cake".
Breakfast items at Flat White include Turkish toast with spreads (£2.25), bircher muesli (£3.50), porridge with sultanas (£3.00) and toasted banana bread (£2.25), which got rave reviews from one user on WeLoveLocal.
The cafe also supports local artists by displaying and selling artwork and music. It's open from 8am weekdays (9am weekends and Bank Holidays), so it's a perfect pre-office pit stop if you work in town. Just don't ask for a cappuccino.