‘Cool Hand’ looked in trouble early on when dropped by Mendez after failing to listen to his corner’s instructions but soon settled down and got into his rhythm.
Overall, it was an assured performance from Campbell who was comfortable against a dangerous and seasoned operator in Mendez as the 2012 Olympic gold medallist pushes for a world title shot in 2017.
Mendez proved shot-shy from the knockdown onwards and Campbell saw out the victory 117-110, 116-111 and 115-112 on the cards
The 28 year-old proved that he is already above and beyond domestic level and could either go the European route next or even a final eliminator for one of the current divisional belt holders.
Earlier, slick Yorkshireman Tyrone Nurse retained his British super lightweight belt in a twelve round war with Hull warrior Tommy Coyle.
Nurse was on top over the first half of the fight and banked the rounds to take a lead into the second six sessions.
A bruised and battered Coyle knocked Nurse down with a straight jab in the seventh round, although Nurse looked more embarrassed than anything and came back strong in the next round.
Coyle probably shaded the later rounds but it was the champion who was given the nod 116-112 and 115-113 twice on the scorecards.