Watford completed the signing of Ben Foster from West Brom on a two-year deal while also adding Sweden international Ken Sema.
The 35-year-old is well known to the Vicarage Road faithful after spending two consecutive seasons on loan with the Hornets from Manchester United during the 2005-06 and 2006-07 campaigns.
In those seasons he helped Watford to promotion to the Premier League and was their starter in goal for their 2006-07 top-flight campaign, though the club finished bottom of the table and was relegated.
He returned to Manchester United, where he was used sparingly over the next three seasons, before a one year stint at Birmingham City ahead of his eventual move to West Brom.