Poppy Gustafsson, the co-founder and chief executive of the British cybersecurity firm Darktrace, is to leave the company after its $5.3bn (£4.2bn) sale to the US private equity business Thoma Bravo.

Gustafsson, one of the best-known figures in the UK tech industry, founded Darktrace in Cambridge in 2013 with backing from the late billionaire Mike Lynch’s Invoke Capital.

In April, Thoma Bravo, which walked away from previous takeover talks in 2022, agreed a deal for the London-listed company that had been considered by analysts to be undervalued by investors.

Gustafsson is to step down with immediate effect and will be replaced by Jill Popelka, Darktrace’s chief operating officer.

“Darktrace has been a huge part of my life and my identity for over a decade and I am immensely proud of everything we have achieved in that time,” said Gustafsson, who was awarded an OBE for services to cybersecurity in 2019. “Now is the right time to hand over the reins so Jill can lead Darktrace through its transition into private ownership and beyond. I remain Darktrace’s number one fan.”

Like many of Darktrace’s management and key staff, Gustafsson, who co-founded the firm when she was 30, was a former employee at Lynch’s software company Autonomy.

Hewlett-Packard sued Lynch, alleging that he duped the US company into overpaying when it struck an $11bn deal for Autonomy in 2011.

HPE won a civil claim against Lynch in the English high court in 2022, but the tycoon was cleared of fraud charges in a US court in June. The 59-year-old and six others died last month when a superyacht sank off the coast of Sicily in a storm.

In 2018, Darktrace was subpoenaed by US authorities for information about Invoke, warning there was a risk of money-laundering claims if its backing money included cash generated by the Autonomy sale.

Gustafsson, whose favourite mode of transport is said to be a canary-coloured Vespa, floated Darktrace on the stock exchange in 2021. Shares have risen more than 70% over that period.

Lynch and his wife, Angela Bacares, held a 6.8% stake in Darktrace that was worth £300m at the time of the sale.

Gustafsson has been a champion of gender diversity in tech, an industry that, in the UK, is more than 70% male in terms of employment compared with a broadly 50/50 split across the wider economy.

Three out of 10 of Darktrace’s 2,400 employees are female, in line with the industry average of 29%. Gustafsson has spoken in the past of being at industry events and seeing “a sea of men staring back at you”.

Her departure will reduce the number of female leaders in the UK tech industry, where women occupy just one in five senior roles, according to a recent industry survey.

Darktrace’s time as a publicly listed company has been dogged by controversy and a number of short-sellers and analysts have criticised the business model as sales over substance.

Between 2022 and 2023, the short-sellers Shadowfall and Quintessential Capital Management (QCM) published highly critical reports. The latter alleged that questionable accounting and sales practices were used to drive up the value of the business before its flotation in 2021.

Analysts at the UK investment bank Peel Hunt published a report in 2022 citing anonymous Darktrace clients calling its products “snake oil”.

The attacks, which led to Darktrace’s share price plummeting to record lows, prompted Gustafsson to publish a 1,200-word defence of the company last year in which she said it was run with the “greatest integrity”.

Gustafsson grew up in Cambridgeshire, where her father ran an agricultural sales business and her mother was a journalist for Farmers Weekly.

After attending Hinchingbrooke secondary school – alumni include Oliver Cromwell and Samuel Pepys, and the Wolf Hall author, Hilary Mantel, was patron of its 450th anniversary – she took a maths degree at the University of Sheffield, where her first student job was building kitchen cabinets.

She then qualified as an accountant at Deloitte before working for Amadeus Capital, the venture capital company run by Arm Holdings co-founder Hermann Hauser.

In 2009, she moved to Lynch’s Autonomy.