The 20-year-old passed a medical and will now join The Baggies’ first team squad with immediate effect, and be eligible for his debut against Norwich on Saturday.
Allan’s contract at Tannadice was expiring, and with the starlet set to become a free agent in the summer, the Scottish side decided to cash in on their young talent.
Old Firm duo Rangers and Celtic were also thought to be interested in signing Allan, but the news of his departure to Roy Hodgson’s outfit was confirmed by United manager Peter Houston.
“I’d like to wish Scott all the best for his future career, it is a fantastic opportunity for him to go down to the English Premier League,” the coach told the side’s official website.
“The completion of the deal at this time was beneficial for both the player and the club.”
By Gareth McKnight