You start with online tests, mathematical and data interpretation which are generally standard.
Then it's pre-recorded interview questions, you get 30 seconds to consider the question and then a minute to answer it. This is tough as they cut you off after a minute so try and keep your answers to a paragraph or two when preparing them.
From there you're invited to a Selection Day. This is quite intense, it begins with a presentation on how great Newton is, then you give a 3 minute presentation that you prepare before hand. This can be on absolutely anything, just focus on having a clear structure and message and you'll be fine, we had somebody talk about his love for one football club, another on gymnastics etc... They say no visual aids, so you have to learn it and make sure you are 100% sure on what you're saying and make sure it fits within the time frame.
Then it's a case study, ours was on decoupling processes in a factory to improve efficiency. The idea is easy enough to understand but the questions that follow are, inevitably, more complex - 3 questions each with several parts. Ours considered a company that already had a decoupled process and you had to suggest ways to improve it, what speed it runs at etc... Try to avoid dwelling on one question here, look at them all and then decide which ones you can answer quickly and go from there.
Then you redo the tests that you did online, different questions but the same idea. Some advice, only the maths test is non-calculator, so bring one along for the rest of the day.
Then you have a 1:1 interview but, as others have said, this seemed more like a chat. I was asked what brought me to applying to Newton, what skills I can offer and where I might improve, and an example of a time when I struggled with something or found something difficult. Again, it was quite informal so don't fret on it too much.
After that it's a group task using stationary to separate a couple of pens or whatever. It's the process not the result that's important. I was the only one from a non-engineering background in my group so I used the skills I have and let them focus on designing things. After all, knowing your colleagues skills vs your own is a big part of teamwork.
Then we had lunch, I was fortunate enough to get through to the afternoon although I was the only one which certainly made the process a lot more intense.
The afternoon involves another Teach session, this time it was on line efficiency and how to measure it, how to compare it etc... Again, the concepts weren't too difficult, if you're from a business or economics background I think you have a bit of an advantage here as it focuses a lot on profits and potential profits etc...
Then you have 40mins to prepare for a mock meeting with a potential client, they give you lots of information and you have a few key questions to prepare answers to. I fell down here as I spent too much time on one part and neglected the important stuff, like potential profit. You then meet with the clients, present your findings for 20mins or so and they grill you on them so have your notes laid out clearly in front of you, ready for questions like: How did you get that number? Can you explain your reasonings? Also focus on ways to improve the business.
Finally you have to do a physics/mechanics test. Was completely outside my skill set but they claim it is only formative, though I can't really see that being the case. Why give a test if it doesn't have any baring?
Overall it was a mentally exhausting day, certainly the toughest AC I've done, but it was a good experience and they are a great company. Will apply again if I am in a position too.
