I applied online. The process took 1 week. I interviewed at Deliveroo (Guildford, England) in Jun 2016
Interview
Applied online, got a call 5 minutes later, confirmed everything in application, scheduled a trial shift, cycled for a bit confirming I knew what I was doing, picked up kit 3 days later with 3 other people also, started that evening. Didn't get asked very many questions, most of it was telling to what to do.