I applied online. The process took 1 day. I interviewed at American Express (London, England) in Dec 2016
Interview
Told what was occurring a few weeks before the assessment centre, nothing to prepare for in advance, just revise your competency questions and research the company. Very friendly staff and sympathetic towards nerves (because as assessment centres go, this was early, so everyone was a first-timer). 2 competency interviews - 1 scenarios and other motivation for Amex and B/d. 1 group case study - prioritisation and contribution are key here. 1 individual presentation - study for 45 minutes and present for around 10. Breakfast, networking and lunch. All around a good day, requires focus throughout the day.