1) HR prescreen. HR will ask you 1) Are you a British Citizen 2) We will require a non-HR professional reference. The notion of a professional reference seems outdated, however Zaizi does government contracts, so it would be excusable for its outdated procedures.
2) Quick chat with an actual engineer. Just a gauge to see if you actually worked in tech before. CV based and some Computer Science concept questions, no actual coding questions.
3) A presentation. You will given a topic and then you need to deliver a presentation on it. You have 2 days to prepare.
The CTO didn't really look at me during the presentation, and seemed preoccupied with another screen or possibly his phone. He has no interest in you from the very beginning despite all your efforts. Very unprofessional.
