Started with a relatively long build a CV process, then some interesting aptitude tests based around identifying black box functions. This was followed by a HR interview with an external recruiting agency, and then a fairly simple offline programming task, which I had a few days to write and submit. I then had a conference call with two pleasant (although hard to understand due the poor connection) BT engineers talking about my solution, what choices I made, what I could have done better. Several weeks later I received an invitation to an assessment center. However I was only given one day's notice and they wanted me to research and give a presentation on potential business ideas for BT. Due to the short notice, non-technical nature of the assessment center and changing personal circumstances, I withdrew at this point.