Ah, finally figured it out. I once worked in le 8ème, which presumably scuppered DS' chance of an Oxbridge place. Brexit is too recent. Perhaps Diana? Or do dons' memories stretch back to De Gaulle or Napoleon.
Surely at the end of the day, Oxbridge re-applications reflect what you might do in real life. You don't get a job. Another similar vacancy is advertised. You don't apply because you have decided your application was not strong enough, or because the competition was so intense, or you have found another good job. Or you reapply because the job is the perfect next step for your career and/or in the right location, and you can see ways of strengthening your application or suspect you were a near miss, and think things might go your way this time. As far as I can tell Oxbridge do their best to give all home/EU applicants an equal chance, as they are required to do by law.
7214743615 is correct. Many of DC's London contempories were happy to shrug their shoulders and head off for Imperial/UCL/LSE, where they are confident of an interesting, stretching education. However this is harder for students from outside London who do not find the thought of student life in London attractive. Others decided that an extra year was not much in the scheme of things, and so had another go. Including some like Orlanda's DS who failed to land a place on any of the very competitive courses first time round. Our observation has been of a good success rate on reapplication, but these were usually credible rather than "have a go" candidates. And even if a student does not get a place, the extra year's maturity can mean you are more University ready, wherever you go. (And specifically perhaps, more ready to live in London if that is your alternative.)
I wonder if Bob's worries stem from British Universities looking for different things. So "strong" French candidates may not do as well in the British application process, whilst others, considered weaker, land places. Bob has previously complained of an LSE bias against the French, but I have been assured that French is the third most commonly heard language in LSE corridors, after English and Mandarin, so someone is getting in.
As to a bias against public schools, DCs school was never convinced. They sometimes had bad years for specific subjects, where very strong candidates did not get places, but things generally balanced out. Candidates did need to be at the top of their game, and competition for some subjects (E&M, NatSci, Engineering, medicine, law, engineering etc) was such that there could not be a place for every strong candidate. But hey. Apply again or go somewhere else good. Again Bob's problem seems to be that her clients won't consider places outside the London-Oxbridge triangle. But then again they may well have different fall-backs in the US, Canada, or France.