Worst interview experience I had in my life. HR is a central decision maker in this company and if they don't like you, that will be a final decision, not your manager's or CEO's. They would normally take you through 6-7 stages, some of them are non-sense irrelevant economic and maths tests. You can expect to get a job offer which will be withdrawn later without any explanation and you will not even know about the fact they started looking for another candidate in parallel. If you get an offer from Octopus, keep looking for jobs until you first day with them, as they change their minds.

Be warned - they fool you into thinking it's just one more interview - 10!!!! Phone interview followed by face to face x 4, including HR, followed by a further 2, followed by a further 4. Make up your minds guys - that's at least two man days effort. What exactly are you gaining - it's not going to prevent you employing time wasters as proven by the process.