Mobile-first financial services startup Atom Bank is closing in on £1bn in deposits, less than two years after it launched its first product.

The app-only bank has confirmed that it has received more than £900m in deposits since July 2016 when it launched its first savings accounts. It has amassed close to £400m since March.

“Responsible and sustainable growth of our business has always been a priority for Atom, passing on the benefit of our low-cost model to UK consumers in the form of competitive rates,” an Atom spokesperson told Business Insider. “Our savings deposits have now grown to over £900 million, with our mortgage and business lending following a similar trajectory. We’re the fastest growing challenger bank in the UK, with cost and efficiency driving our ambition to deliver great value for customers and investors.”

Atom was founded in 2014 in Durham by Anthony Thomson, co-founder of Metro Bank, and Mark Mullen, former First Direct CEO. Earlier this year, the bank sought to differentiate itself from the competition with the addition of US musician and founding member of the Black Eyed Peas, Will.i.am, as a strategic board advisor.