Watford have completed the signing of former Dundee United midfielder Prince Buaben on a two-year deal.The 23-year-old left Tannadice at the end of last season, following the expiry of his contract.He joined United from Ajax in 2007, and went on to score 11 goals in 142 appearances while in Scotland.The Ghana international is a product of the Amsterdam side's youth system, but did not have the necessary resident's status to sign a professional deal.Swansea, Brighton and Aberdeen were reported to be interested in signing the central midfielder.Source: BBC