Danny in the Valley

Slack co-founder Cal Henderson: 'Email is the cockroach of the Internet'

The Sunday Times' tech correspondent Danny Fortson brings on Cal Henderson, co-founder and CTO of Slack, the wildly popular business messaging platform, on founding photo sharing company Flickr (2:30), its ill-fated sale to Yahoo (6:00), starting again (9:00), the accident that became Slack (10:30), being a unicorn (14:30), his early days in London…