Mellor is likely to go straight into the Hammers side for the opening game of the season at Preston on Saturday.
"I am absolutely delighted, very excited about the season ahead and the challenge for myself," Mellor told the Hammers official website.
Mellor is likely to go straight into the Hammers side for the opening game of the season at Preston on Saturday.
"I am absolutely delighted, very excited about the season ahead and the challenge for myself," Mellor told the Hammers official website.