Bull downs tasty triple; Grimsby 1 Wolves 3.
Grimsby had nothing to show for their initial territorial advantage and they had to take a back seat as Bull gave them a sharp scoring lesson.
And he received good support from his new pounds 1 million partner Iwan Roberts, though the Welsh international suffered a head injury in the second half.
Wolves manager Mark McGhee said of Bull afterwards: "He has looked sharp and at his best during the week. Now he's scored three goals and you can't argue with that."
Steve Froggatt also impressed on the left as he laid on all three of Bull's goals and gave Grimsby player-manager Brian Laws the run around.
Although Andy Thompson threatened with an early overhead kick, Wolves had to withstand a stream of pressure from the Mariners in the first half. Former England star Neil Webb prompted them from midfield and when he won possession after 15 minutes the ball fell for another newcomer, Kingsley Black.
The Northern Ireland international winger found himself in the clear and forced the first of a series of brilliant saves from Mike Stowell
Bull had a header blocked at the other end, but the Mariners continued to threaten and Neil Woods headed just over.
However, Wolves made the breakthrough after 36 minutes. Froggatt got the better of Laws on the left and knocked the ball across to the unmarked Bull, who flicked it home.
Wolves had Dean Richards booked and Stowell saved well from Webb, but then the combination of Froggatt and Bull struck again a minute before the break.
Froggatt unleashed a long ball that caught the Grimsby defence square and Bull raced through to lob the ball coolly over keeper Jason Pearcey from 30 yards.
A minute into the second half Bull was denied by Pearcey. The keeper, though, let himself down with a poor kick and had to watch anxiously as Thompson's shot rolled just wide.
But then the keeper smothered a header from Bull and denied him yet again with a flying save to his left to keep out a vicious drive.
Wolves looked in little trouble, but after 62 minutes Webb conjured a goal out of the blue for the Mariners.
Clive Mendonca took his pass and was allowed to turn in the area before shooting home.
But the ebullient Bull was not to be subdued and his hat-trick goal duly arrived 19 minutes from time.
This time, Pearcey had no chance as Bull lashed in his shot from 10 yards after being allowed to control a cross from Froggatt.