The process took about 5 weeks. Initially I had a phone interview with a senior member of staff asking about what I know about Dunnhumby, skills and projects I worked on in the past. After I got word of progression the next round was a numerical reasoning test. This was difficult but a few days preparation before hand and you will do well. I was then invited into their London HQ in Hammersmith for a face-to-face with two senior staff. The interview itself was very pleasant. It lasted about 2-2.5 hours but I didn't even notice the time go by. I had to do a case study and give presentation on the topic. They sent on the case study a week prior to the interview and then they asked me general data analysis/science questions on the study. There was also a coding exam which was relatively straight forward. They didn't require you to write the code in any specific language as such more about the algorithmic process. A few weeks practice on HackerRank will help you here. Although the coding exam was straight forward I didn't actually perform well on this as I never done a coding test before and through a mix up between my recruiter and HR I was told there was no coding exam. I got the refusal phone call about two days later and was told my coding ability wasn't up to the threshold they required. Overall it was a very nice experience as this was my first ever data science interview. It's a shame I didn't get the job because I really wanted to work with them. Once I get a little more practice and experience under my belt I will definitely apply again.