Charl Schwartzel cruised to victory in the Tshwane Open on Sunday to claim his 11th European Tour title and an eighth on home soil in South Africa.
Pre-tournament favourite Schwartzel held a one-shot lead heading into the final round and carded a closing 63 to finish 16-under-par at Pretoria Country Club, eight shots clear of Jeff Winther.
Lombard began the day just a shot behind Schwartzel but double-bogeyed two of the last three holes in his 74 to finish 12 strokes adrift, while Joburg Open winner Porteous struggled to a 73.
Schwartzel made the ideal start with a birdie from 18 feet on the second, only to bogey the third after a wayward drive finished behind a tree and meant the South African could only find a greenside bunker with his approach.
However, the former Masters champion responded with birdies on the sixth and seventh and then holed from 10 feet for an eagle on the par-5 ninth for the second day in succession.
The world no.43 dropped a shot on the 11th after a wild tee shot and was lucky to get away with another on the par-five 12th, but any lingering doubt about the outcome was ended with a birdie from 40 feet on the 14th.