How I Created Two Billion-Dollar Fintech Startups

Blomfield began building websites for local businesses at 15, then studied law at Oxford while starting an online student marketplace. After graduating, he joined a YC batch with a bill-splitting idea, which the team pivoted into B2B payments and GoCardless. YC reset his expectations for the quality of ideas and execution required.

GoCardless grew slowly as the team added customers, but Blomfield left after three years because its problem did not feel personal enough to keep pursuing. He wanted to take on a larger challenge, and in 2015 he and his co-founders started Monzo to make banking software easier to use. They launched a prepaid-card prototype within three or four months, and word of mouth helped Monzo reach one million customers in about two and a half years.

Blomfield says Monzo’s ambitious goal attracted talent, press attention and customers, while a simple user experience encouraged referrals. Rapid growth also brought financial crime investigations, threats, outages and intense scrutiny because customers depended on the bank for payments and paychecks. During COVID, card revenue fell by about half and a planned £100 million funding round was withdrawn shortly before closing.

Regulators urged Monzo to prepare to wind down while the company was losing £100 million a year. Blomfield described working long hours, struggling to function and finding that his identity had become intertwined with the company. He stepped back, and the new CEO, COO and executive team continued leading Monzo, which he says later grew to more than eight million UK customers and became profitable.

After a year off, Blomfield began advising founders and made about 75 angel investments in nine months. He joined YC as a visiting partner and later became a group partner. He describes the role as a chance to give back by helping founders tackle difficult problems and build businesses.