“I was talking with a user in a seminar about one of the major banks, and I asked him what he thought of their app. He said they didn’t have one. So I searched it out for him and he said, ‘No that’s not the official app, that’s phishing.’ He actually thought the design was so poor that it must be something dodgy. That was a big epiphany for me: that a customer could be so confused about whether the app you’re offering is real or not.”

Hugo Cornejo is head of design at Mondo, one of four small challenger banks—alongside Atom, Tandem, and Starling–making waves in the UK’s financial sector. Unlike global giants like HSBC, RBS, Citibank, and J.P. Morgan, these young upstarts are placing an emphasis on seamless technological integration, real-time access to financial information, and predictive banking that helps limit charges and fees.

“Most banks’ business is not in helping you,” says Cornejo. “It’s about making more money. Our business is completely different. We’re still going to make money out of lending, but we want you to be in control and anticipate things so you can make informed decisions. We’ll tell you that if you keep spending with this pattern, in a week’s time you’ll have no money left. Or we can offer you an overdraft, but that overdraft will happen without punitive fees or any of that kind of crap.”

Currently Mondo is limited in the services it offers. Until sufficient funds are raised to earn a full banking license, standing orders, direct debits, mortgages, and loans are off the cards. While that may seem prohibitive to launching products, Mondo has used the opportunity to user test and innovate within strict limitations.

While they still only offer a pre-paid, contactless debit card (a system that, like Apple Pay, allows for one-touch purchasing) integrated with an iOS and Android-enabled app, Cornejo tells me the system has already found favor with a hoard of London’s design and tech community, largely for the clarity and functionality of the design. The real-time element, too, has proved to be alluring; when making purchases with the card, the app immediately notifies users and updates their live balance accordingly.

Cornejo is acutely aware of the fact that a bank cannot run on the earnings of London’s designers and developers alone, and Mondo’s rigorous user testing is designed to ensure universal usability. “We have a big bias because we’re in Old Street with all the young tech companies, and our users are really tech-savvy nerds. That allows you to get away with things that the rest of the population wouldn’t allow. So we need to be as conservative as possible in our design and make sure that 99% of the app is something everyone can use.

“User testing works partly as a validation of things that we’re not sure about, and it’s good for our culture of sharing all that we do. We wanted to make sure that what we were building was worth it, because what we’re doing should be really interesting and useful, and if it’s not, we want to be able to correct that. There’s lots of learning to be done by releasing something early and playing with your users.”

Recently this playful approach and willingness to engage its community has rescued the bank from minor legal issues. Challenged over the rights to their name, Mondo invited its users to choose a new moniker under which they would rebrand.

Similarly innovative is its approach to banking software. Most banks currently operate using “slow, monolithic systems that can’t grow beyond a certain size.” Mondo is building its own, from the ground up. This, says Cornejo, will facilitate upscaling to a degree that existing banks can’t even imagine, potentially enabling a user base as large as that of Facebook or Instagram.

Given the scale of their ambitions, it’s surprising to discover that Mondo’s design team has only three members, another clear reflection of its start-up status. Cornejo insists this is enough, and that their combined experience is sufficient to build a new bank from scratch. Cornejo himself already has a pedigree in the financial sector, having designed systems for a Spanish bank to streamline their internal communication of complex statistics and data. Here he learned the key design principles that are now at the core of Mondo; the presentation of synthetic and analytical data, and the merging of digital and analog processes. “We don’t do anything ‘just because.’”

This kind of user-orientated approach is essential for a young company asking their customers to trust them with their life savings, but Cornejo has simpler design concerns, too. “I bank with Natwest,” he says, “and I even hate their icon, I don’t want to have it on my phone. On the home screen I have all these nice icons and the banking one is hidden in some folder somewhere. That’s a small thing, but it’s important. How can you be one of the apps that people want to have on their home screen?”

The answer seems to be combining universal aesthetics with exceptional functionality, thorough user testing with strong community engagement—and when you’re unsure how to make the next move, by letting your users decide.