Graylag Goose

This Graylag Goose was swimming near the parking lot at Fernhill Wetlands on Jan 2. I'm a little confused by these geese. This appears to be an obvious domestic goose based on the size of its hind quarters, but my searches on the web were unsatisfactory.
Many of the sites I found were based in the U.K. and usually described the birds as ancestors of European domestic geese. The geese on these sites looked very similar, to the one in the image above, but their hind quarters appeared to be smaller. I didn't find a lot of information on U.S. sites.
My assumption is that there are both domestic and feral versions of these geese and that what we have here are escaped or released domestic varieties.