Bruce Daisley, Twitter’s most senior executive in London, has quit as vice-president of Europe, the Middle East and Africa after eight years.
Daisley, who is British, joined from Google’s YouTube in 2012 and was instrumental in building Twitter’s presence as its UK managing director and then vice-president of EMEA.
His departure, which he announced – appropriately – in a series of tweets, came as a surprise on the first Monday of the new year, when many people were returning to work after the Christmas break.
"This week I reached a milestone of 8 years at Twitter," Daisley wrote. "I decided it's time for a change… so today was my last day.
"I feel so lucky to have worked on a product I love with the best people in the world. What an honour."
Daisley, who published The Joy of Work last year, went on: "I’m going to take some time off. My book is out in paperback [in the UK] next week, and out in February (called Eat Sleep Work Repeat) in the US.
"If anyone is doing anything to fight climate change and wants someone to help them for free PLEASE hit me up."
Daisley is one of the most high-profile and accessible leaders in the UK online ad industry.
Under his leadership, the UK operation became Twitter’s largest market by revenue after the US by the time of the company’s stock market float in November 2013 and Campaign named Twitter as its Medium of the Year in the same year.
Daisley recruited a cadre of strong UK leaders, including managing director Dara Nasr and director of planning David Wilding.
Twitter UK has been shortlisted for Sales Team of the Year at the Media Week Awards on multiple occasions over the past eight years.
Daisley’s team also had to contend with scrutiny from the UK press and users as Twitter faced questions about abusive comments on the platform and the company struggled to keep pace globally with Facebook in particular.
A former Emap executive, Daisley has appeared to look beyond Twitter in recent years as he carved out a sideline as an author and speaker on workplace culture.
Twitter has not immediately lined up a successor and referred Campaign to tweets by Sarah Personette, vice-president of global solutions.
Personette wrote in response to Daisley: "Thank you Bruce for all you have done for Twitter Client Solutions and for Twitter over the past 8 years!
"You’ve been a true partner to me, the entire global team and to our client partners around the world.
"As for what’s next, I’ll work with our leadership team to find the next lead for this amazing team."
A Twitter spokesman declined to comment further.
One industry source said: "Culturally, Bruce has done so much to distinguish Twitter from other tech companies in the UK. That whole ‘bring your whole self to work’ approach – he lives and breathes it.
"Eight years is a good run and there are probably not any other bigger roles for him in London at a Silicon Valley company like Twitter."