So, if you are not working in a large organisation with a HR dept. to do the recruiting; its a small organisation where everybody is under time pressure to do the chargeable hours, achieve billing targets and recovery rates, with clients ringing up asking complex, technical questions all the time, how would you select 2 people out of 400 - all of whom are graduates and apparently qualified to do the job? You certainly do not have time to interview all 400 of them.
You start by writing a proper person specification so you’re not relying only on CVs. You ensure that person specification enables to you evaluate experience or aptitude for all the things that are important to you, so that you can score appropriately and interview the top cut. You can get a huge amount from a two-page personal statement.
My HR department do not get involved in anything but the logistics of most recruitment. The actual selection process is (rightly) down to hiring managers. Our processes do ensure anonymised applications, which is a good thing.
You invest time and effort in selecting the best possible candidates. As another poster pointed out, one reason for productivity underperformance is lack of investment in the workforce. However that isn’t limited to lack of training, it works right back to job design and recruitment.
You don’t use ‘too brown, too poor, probably the wrong accent’ as your recruitment filters. Apart from being appallingly bigoted, you are unlikely to be getting the true best talent - especially because, as another poster pointed out, if those people really do come from less advantaged backgrounds, they are likely to have shown greater tenacity and resourcefulness to gain the same qualifications as Crispin and Tabitha.