Roman Christianity, as established by the Empire disappeared for over a hundred years. However, in the celtic lands, Christianity still flourished but with out connection to Rome. It was Pope Gregory who sent out Augustine to ensure that England became a Roman-church strong hold, and to push out all Celtic influences, with the purpose of bringing that Church under the rule of Rome as well.
Yes, I know --- synod of whitby and all that.
But it was either: (1) Joseph of Aramathia (according to legend) or (2) Roman traders (most likely) who planted the initial mustard seed.
My post was somewhat tounge-in-cheek, not a reference to the RCC formal structure.
This is plain false. St. Patrick himself received a papal blessing before setting off on his missions. The Celtic Churches were never independent of or in schism from Rome, and nobody even thought they were such until Anglican propagandists got through mangling history.