Or more likely, they had a mutual agreement until Britain wanted its own thing, so they exit the deal. Seems like something the English would do. We could have called it Brexit or something
It's not a million miles away from the truth. The UK and France were the main advocates behind the ITU, so they got +33 and +44. Which is...fine...but I've not come across why NA got +1, etc. or even why those numbers were chosen at all.