Don't know about Britain but the US also allows passport renewals by mail, so they can't check the photo against your face but they presumably can check it against your previous passport photo.

There is now, there's a system where you use a webcam to do a live facial-recognition check to verify your identity - with a for profit business (because that's what Tories do, make ordinary parts of government into a way to pay out private profits).

That only confirms the person sitting at the computer is the person in the uploaded photo though.

When you first get a passport you have to have your identity confirmed by a professional person with community standing, teacher, policeman, doctor, someone like that.

They do background checks, it seems quite rigorous.

Once you have a passport/driving license they allow you to reuse a recently verified picture in your application to get the other document.