West Ham United are closing in on the signing of Swansea City defender Alfie Mawson, sources close to the Welsh club have told ESPN FC. West Ham boss David Moyes has made signing a new central defender during January's transfer window a top priority and has identified Mawson as his top target. Moyes is keen to bring in signings who have Premier League experience and Mawson fits the bill after impressing at Swansea following his arrival from Barnsley for around £5 million in the summer of 2016. Mawson caught the eye at Swansea last season playing a key role in the Swans' survival in the Premier League and the England Under-21 international has been tipped for a call-up to the senior side. The 23-year-old has been an ever-present for Swansea in the Premier League this season, but he has been unable to help them clear of the bottom of the table.