You are either deliberately misleading people or are ignorant of the UK education system.
Highschool in the uk ends at 16, you graduate with GCSEs. After this there are 2 extra years of education (compulsory in England), you start university at 18 (at the youngest).
Medical schools are competitive and require strong a-level results, typically 3 As (the second highest grade, after A*) [0]. It's a 4 year degree, you then go onto train for another 5 years as a junior doctor.
From the link numbered [1] above, medical school in the UK is normally five years long. Followed by 2 years of Foundation training, and 5-8 years of specialist training, or 3 years if you go into general practice.
Note that the US education system is more expensive though, so becoming a doctor costs more.
> You are either deliberately misleading people or are ignorant of the UK education system.
I don't think either is necessarily the case - he isn't saying it's easy to become a doctor in the UK, he's saying it's easier than in the US, and that's sort of true, if not by all that much.
In the US you also start university at 18 - med school is a 4 year degree you must have completed your undergraduate degree to begin, then you go on to train for 3-7 years as a resident, depending on specialization. Then maybe more for a fellowship.
That said, I've got both doctors trained in the UK and in the US in my immediate family, I don't really see much of a distinction in difficulty of training to be honest but I'm not a doctor myself so what do I know.
This is also a proportion of students who take A levels which is already filtering down to about 38% of the population in that age group (766k 18 year olds in U.K. so about 643k in England of which about 250k take at least one A level.)
So in a normal year that 12.3% of A level students getting 3 A’s is only 4.8% of the age cohort.
Edit: I should add that medicine is about the hardest subject to get into in U.K. (other than vet med which has so few places) and one of the only ones where they expect you to demonstrate suitability beyond academic performance, e.g. work experience in a caring setting. (Source: shared a house with a med student in undergrad.)
Note that the US education system is more expensive though, so becoming a doctor costs more.