UK 38-year-old software engineer to make £ 500m when tech company floats in US

A British software engineer is hoping to raise nearly £ 450 million when his tech company makes its long-awaited debut on the US stock market.

Cal Henderson co-founded Slack's workplace messaging service with Stewart Butterfield, and their business could be worth £ 13 billion if it's listed in New York.

This means that Henderson, 38, who owns approximately 3.4% of the company, could hold a stake of up to £ 447 million.

Windfall: Cal Henderson co-founded Slack's workplace messaging service with Stewart Butterfield, and their business could be valued at £ 13bn if it's listed in New York

He has a degree in computer science from Birmingham City University but has been living in North America since 2003.

He got his first job across the Atlantic at the computer company Ludicorp, after hacking the company's messaging system and told his bosses that he could help them solve the problems they were worried about.

There, Henderson met Butterfield, one of the founders of Ludicorp, and the two men then established the Flickr photo-sharing website.

Flickr was later sold to Yahoo's tech giant for more than £ 19 million in 2005, making Henderson one of the most successful entrepreneurs in Silicon Valley at the age of 24.

Henderson founded Slack in 2009 with other former employees of Flickr and Butterfield, who created the email replacement service, creating "fragmented silos of inaccessible information hidden in individual inboxes."

Henderson is the head of Slack's technology. The father of two, who grew up in Bedfordshire, is also an author who has published a bestseller book on construction sites.

Slack is part of a wave of highly anticipated tech companies that went public this year, succeeding the Lyft and Uber taxis, the Zoom video service and the Pinterest digital scrapbooking website.