Almost 100% a feral bird.
Take a look at this map showing the movements of a just one bird, which spent some time in Lincolnshire in 2010!
Data taken from the BTO website (http://www.bto.org/volunteer-surveys/ri ... ing-scheme)
Adult 24-07-2005 near Roxton: 52°10'N 0°19'W (Bedfordshire)
Alive (colour rings seen) 02-04-2007 Coate Water: 51°32'N 1°45'W (Wiltshire) 121km SW 1y 8m 9d
Alive (colour rings seen) 25-05-2007 Cassington Gp: c. 51°48'N 1°19'W (Oxfordshire) 80km WSW 1y 10m 1d
Alive (colour rings seen) 02-11-2007 WWT New Grounds, Slimbridge: 51°44'N 2°24'W (Gloucestershire) 151km WSW 2y 3m 9d
Alive (colour rings seen) 09-05-2009 Drayton Bassett Pits: 52°36'N 1°42'W (Staffordshire) 106km WNW 3y 9m 15d
Alive (colour rings seen) 16-05-2009 Watch Lane Flash, Sandbach: 53°8'N 2°25'W (Cheshire) 178km NW 3y 9m 22d
Alive (colour rings seen) 05-06-2009 Coed-Y-Dinas, Welshpool: 52°38'N 3°9'W (Powys) 199km WNW 3y 10m 12d
Alive (colour rings seen) 17-06-2009 Old Moor, near Wath-Upon-Dearne: 53°31'N 1°22'W (South Yorkshire) 166km NNW 3y 10m 24d
Alive (colour rings seen) 18-06-2009 Lagoon 1, Rutland Water: c. 52°39'N 0°42'W (Leicestershire) 60km NNW 3y 10m 25d
Alive (colour rings seen) 13-03-2010 Frampton-on-Severn (Court Lake): 51°46'N 2°22'W (Gloucestershire) 148km WSW 4y 7m 17d
Alive (colour rings seen) 24-04-2010 Frampton Marsh (RSPB): c. 52°55'N 0°0'W (Lincolnshire) 87km NNE 4y 9m 0d