I applied through the O2 careers website. Attached a covering letter and CV. I applied on a Saturday and received a phone call Monday from the internal recruitment team. I had a telephone interview within a week with the recruiter, this was a screening phase. I then had a formal interview 2 a week later with line manager and head of department. There was meant to be a 3rd stage interview, but this was not required as they made their decision in the second round and were satisfied I was suitable for the role. It was a good experience overall as I was updated throughout the process and the recruitment specialist was very professional and supportive.