Wow, the assessment sure has changed. Back in the early 90's when I was recruited, you had 2 group assessments (15 of you planning a trip for an american family onboard..lol) then the party scene, where 3 of you would have to socialize, and you were marked on that. You had a basic maths exam, and then another exam, which escapes me right now as to what it was. Before the assessment, they would place decoys in the waiting room who would be watching you, and listening to your conversations with other applicants. As well they also did the weigh in to determine if you were height to weight proportioned.
The first call back would be for the 2:1 on a different day.
If successful in the 2:1 you would then be called back for the medical, which included a dental exam and HIV test. On the same day you would do a language exam (then you had to speak a European language).
After all that you would wait like a month or so before being offerred the post.
It took me 8 months total to get on with BA!!!!