Is 16 and 20 too big an age gap?

It's legal. So nothing wrong with it. Just probably frowned upon. But it really depends on you; how much you care about others. How much she cares about you.. etc etc.. This is what it boils down to. I always feel if a relationship works it works. As long as it checks all the legal boxes anything can feel and be right and fall perfectly into place. If you were at the same stages in life that is no guarantee the relationship would blossom anymore.

In the United States?  That age gap would land you in prison for 15 years 

Illegal. Ditch it now. She is jailbait. It is not worth it. Have ADULT friends. It is way safer. Trust me. Be friends with people 18 or older only. No minors.

It's a big gap in terms of maturity and life experience. But as you point out, it would be legal to have sex with her in the UK. That would also be legal in the majority of US states too, btw. 

Hey You so beautiful as usual!!

Sorry one more time, I didn't mean it!In conclusion just want to tell you, I never mention your name up there! I wish you happiness! regards,

The age of consent is only about having sex. You haven't even met her yet!

Technically no it's not weird but 16 and 20 are two very different stages of life. One is in the GCSE period and one is at university age. So in that view it doesn't seem right. 

Nah dont deal with those highschoolers, too many fine women in college/university anyways. 

These impact of an age gap changes as the parties involved get older. A four year age gap is nothing if you’re both over 30, but yeah, a 20-year-old should definitely not be involved with a 16-year-old. The power imbalance is way too much.

4 years is not really that big an age gap if it's the age of consent. Consider that girls in general mature more quickly than boys do, so really I'd say that a 16 year old girl and a 20 year old boy are, in most cases, very close in maturity level.