I don't know much about Greylag, she's been on the river for several years, her owner keeps her in very nice condition. She's normally out on the moorings in the river, near where we kept Greta, but presumably she's been brought into the marina to escape the worst of the winter.
Pure speculation on my part, she has the look and volume of a working boat with her transom rudder, but the curved stem suggests that she was built as a yacht, perhaps by a yard which also built working craft?
At first sight you expect her to be gaff rigged, but again the tall Bermudian rig speaks again of a yacht heritage.
That flush deck gives her a very purposeful look and would be a great platform for working sails and anchor gear.