Barclay, currently on gardening leave, will take up the role of regional director for London and Harlow.
"This was by no means planned, but it was a role I was looking to take on when I was originally with Howard Smith," said Barclay.
He replaces Tony Wood, who left Howard Smith in July last year to rejoin former chief executive Martyn Eustace at Premier Paper.
Barclay became managing director of the firm in October 2003, replacing Nick Henry.
He was previously digital manager with Howard Smith, and prior to that was digital general manager at Papyrus.
Ashley Wood, sales director of sister firm Smurfit Townsend Hook, will take on Barclay's duties until a replacement is found.
Hale is part of Smurfit UK, along with Townsend Hook's mill at Snodland.
Story by Andy Scott