Yesterday I caught up with Tom Blomfield, co-founder and CEO of “challenger” bank Monzo.

The startup is building a digital-only bank, or “smart bank,” as Blomfield calls it, and last August was granted a U.K. banking licence “with restrictions” by the U.K. regulators FCA and PRA, as it prepares to launch a full current account later this year.

It’s the hardest thing I’ve ever done in my life Monzo CEO Tom Blomfield

As it exists today, Monzo’s more than 100,000 users get access to a pre-paid MasterCard and accompanying iOS and Android app. It offers the ability to do things like track your spending in real time, view geolocation-marked transactions on a map, view spending by category and get a graphical timeline of your overall expenditure.

In our call, we talked about why Blomfield and his 80-plus team are building a new bank, whether or not we are in a fintech banking app bubble and what he thinks the impact will be of upcoming PSD2 EU regulation intended to force incumbent banks to open up.

Candidly, he also confirmed that Monzo has already turned down an acquisition offer from a major bank, and explained why he thinks it would have been a mistake to sell.

You can listen to a lightly edited version of the interview below.