City's two goals came less than two minutes apart in the 12th and 14th mins. Kimbo heading the opener and soon after Kim set up Campbell to make it 2 - 0.
it was a frantic opening with chances at both ends.
Brentford managed a few decent efforts with Lewis producing a stunning save before the Brentford attacker headed over from close range.
The Bees reduced the deficit with a cool slotted finish just before half time.