> He entered Oxford University at 17 without A-levels and left around a year later without graduating. He was bored and he had been invited to cross the pond by the prestigious California Institute of Technology (Caltech) to do a PhD. "I had written a bunch of papers and so was pretty well known by that time," he explains.
Is it still possible today? Yes. Alessio Figalli is another example, from 2006-2007, and Glen Weyl in 2007-2008.
It's very rare.