I too was involved with graduate recruitment to an International company and we did a first sift on a combination of academics, GCSEs, A levels, (predicted) degree class as well as evidence of outside activities, work experience and positions of responsibility etc. That did tend to push through Oxbridge applicants more than say non RG unis simply because they were the ones with the academic results that got them into Oxbridge in the first place Then the main process was based on identifying evidence they had ability and personal qualities in 8 main areas we had researched to be important to success in the organisation, 4 personal and 4 intellectual, through psychological testing, role playing and team exercises, case studies and interviews. Clearly the way someone talked or dressed (within reason) did not count as evidence of anything. At that stage it was very much about personal qualities and the graduates we took on were a complete cross section, we didn't engineer diversity but we did monitor it and on the whole achieved it. It's quite a common model for recruitment and used in DHs bank.
I completely disagree with Russians on international outlook having lived and worked in as well as studied a different culture, one perfectly capable of delivering shitty experiences as well as being fascinating. I have watched representatives of UKPLC operating there with an utter ignorance and disregard for the culture that put them at a serious disadvantage (including David Cameron). On the whole I think that lawyers and bankers, having to get involved in intense high stakes negotiation, quickly learn the skills they need to operate but I always felt like I was operating with one hand tied behind my back. Though I aimed to be culturally sensitive I realised after studying that culture deeply back in the UK that I had nethertheless been looking at everything from a western perspective, and it was a bit of a road to Damascus. I would approach my job quite differently now, but then I found it all so fascinating I have never really gone back to the day job 
The graduates who emerge from my uni really do understand the cultures they hope to work in and do very well in the job market, including women to practise law in the Middle East, having been taught by some excellent role models. My DDs though having spent formative years in another culture just don't even need to engage with the issue intellectually. They are totally adept at operating within different cultures and both have a multicultural group of friends, they don't see themselves as "British" but global. en.wikipedia.org/wiki/Third_culture_kid
I do think from experience and our outreach activities that this is one area in which state schools have a way to go. When we came back from overseas the indies were falling over themselves to make it clear that they really valued the DDs overseas experience, the state schools were entirely disinterested, though perhaps that was because they knew we wouldn't get a place as late applicants. Candidates from state schools to our uni tend not to have quite such strong applications in terms of their curiosity about the culture, and it doesn't have to be a gap yah, or travelling with the rents, reading books and newspapers can demonstrate equal intellectual curiosity. Ironically some of the schools we visit are very multicultural, I suppose if the schools are not encouraging them and equipping them to make university applications, it is far too much to hope it would be opening their eyes to the prospect of studying another culture. My point is demonstrated by the phenomenon of Mandarin teaching in schools, lots jumped on the bandwagon far outstripping the supply of good teachers, and then many jumped off it again. Few schools have robust strategies in place for effective teaching of Mandarin, and most of those are indies.
The lack of opportunity to study MFL in state schools, our local comp plans to offer none at A would certainly hamper state school applicants to DH's bank as they require a knowledge of 2 languages, at least one to speaking standard.
Finally, sorry very long winded word factory I have worked extensively with banks and law firms and I really do think the overnighter thing is 70% to do with culture, 30% need. Decent project planning and business management skills, albeit as much on the client side, really can reduce the need for all those long hours. When my friend persuaded her fellow partners to let her go part time she met with huge resistance, and yet her clients had no problem and her chargeable hours were amongst the highest in the partnership. It wasn't the demands of the job that drove her into the public sector, it was the attitudes of her fellow partners which were largely the result of the fact that putting your head down and getting the job done 9-6 wasn't valued in their cultural paradigm. I accept city law firms are running very tightly but at least one of my peers can routinely be seen at the station at 11am, just because he chooses a 12 hour day that ends at 11pm, it scarcely seems fair to inflict that on others in his department. My DH is at that station at 7am so at least he sees his DDs before bedtime, but don't get me on the long term impact of that culture and those hours.....
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Really gone on here but you touched a few nerves 