Mark Mullen was chief executive of First Direct, the telephone and online bank, before he moved to Atom. News of his move to lead the new digital bank came in April 2014.
Atom was founded in July 2013 by Mullen and Anthony Thomson, who also co-founded Metro Bank. It won a full UK banking licence in June 2015 and launched to registered users in April 2016 with no branches. BBVA agreed to invest in November 2015.
Under Mullen the bank raised £75m in February 2022 at a £435m valuation and £100m in November 2023 at £362m. Atom introduced a four-day week for 430 staff in 2022. In 2024 it made its first annual pre-tax profit since launch, with revenue of £99.1m.
In early September 2026 Mullen stepped down as chief executive. Andrew Marshall, the chief financial officer, became interim CEO on 4 September, and the board began a search for a permanent successor. Mullen said he would support the company until the end of 2026.