They have to do a KYC (know your client) check, which I assume they do a credit check on you, probably via Experian or another one of these. You also send a picture of your ID, and record a video of yourself saying "Hello, I'm $NAME and I want to open an account with $COMPANY".
The Barclay's part is just an old practice. How I ended up doing it after two months was by having a letter from my employer stating that I'm registered with them at a particular address. But what I learned from somebody else that went through this, after those two months, is that they could have said my "home" address was the address the company is registered at instead. This is how they've used to do it with other people that have hit this problem, it just didn't occur to me to ask for something like this, and it didn't occur to them to suggest this either since they assumed I had everything in order (since I already submitted my Monzo account for salary payments).
The Barclay's part is just an old practice. How I ended up doing it after two months was by having a letter from my employer stating that I'm registered with them at a particular address. But what I learned from somebody else that went through this, after those two months, is that they could have said my "home" address was the address the company is registered at instead. This is how they've used to do it with other people that have hit this problem, it just didn't occur to me to ask for something like this, and it didn't occur to them to suggest this either since they assumed I had everything in order (since I already submitted my Monzo account for salary payments).