All in all there were 4 steps:
First of all had two telephone interviews with a recruitment agency to see if I was suitable for the role. Pretty standard and nothing out of the ordinary.
Secondly, around a week later was another telephone interview. Except this time with the Amazon department head. This phone interview was split into two parts. She firstly asked me when I conformed to three of Amazon's leadership principles and then I needed to go into detail regarding my answers. In the second part I had to play the role of an Associate Vendor Manager pitching the Vendor service to a fictional company (she played the company MD).
The third stage was verbal and numerical online testing (SHL). They give you lots of time for verbal but I personally found it impossible to do all the numerical question within the time allocated. Do lots of practice tests and you should be fine.
The fourth and final stage are the interviews at their HQ in London. I say 'interviews' because there are FIVE of them in one day. The interviewers range from Vendor Managers to division heads. For myself, interview one, two, four and five all revolved around their similar and somewhat contradictory 'leadership principles'. I prepared two examples based on my experience for all 16. I was slightly surprised, however, when (a few outliers aside) collectively they only asked me about 3-4 of them...This left me in a bind as I was soon struggling to remember new and original answers on the spot. The fact that I didn't get an offer because my answers lacked structure was definitely not a surprise. Maybe I was just a bit rubbish too. Interview three is a general Q & A with a member of the team so that you can find out more about the position and Amazon, work/life balance, New York Times article.. etc.
A majority of the interviewers were really nice/experienced and I can imagine them to be great people to work with. I understand that there isn't a formal hierarchy as such in the department which means that everyone is approachable if you need advice or help. Amazon in the UK, especially since their move to Holborn (Slough anyone?), also seems like a good company to work for.
However, the Associate Vendor Manager role itself might not be for everyone. Contrary to what I thought before the interviews at their HQ it seems that an Associate will either be on the phone, doing admin, writing emails or running data analysis (they're very data driven) at least 95% of the time. The room for actual face-to-face contact with Vendors and potential customers I believe is very small. It all seems quite linear with not a huge amount of variety. I could see myself struggling in that environment but for others who like a set schedule then I would say go for it.