The intensity and tempo dipped after the 70-minute mark, though Palace continued to monopolise possession and, in truth, the visitors could not get near them. With chances becoming more sporadic, the closing stages provided a welcome opportunity to hand minutes to Khyan Frazer-Williams, Raihaan Anderson and Mylo Bernard.
As the game entered its final third, Bernard was slipped through one-on-one by Anderson but dragged his effort wide of the target. At the other end, Benetton remained largely untroubled throughout, a fact underlined by Birmingham winning their first corner only in the 77th minute.
The contest had long since been put beyond doubt and, although the Blues offered the occasional warning sign of pulling one back, they never seriously threatened.
With ten minutes remaining, substitute Frazer-Williams intercepted possession and embarked on a marauding run before unleashing a venomous strike from distance that rattled the crossbar. Benamar and Okoli then both saw efforts blocked by desperate defending.
Palace continued to probe in search of a sixth, with Birmingham forced to withstand a succession of shots and crosses. In the dying moments, Martin was denied a hat-trick when he turned in Okoli’s first-time delivery at the back post, only for the assistant’s flag to rule him offside.
The result sees Palace climb to second, level on 27 points with Tottenham but boasting a superior goal difference, while remaining six points adrift of leaders Chelsea.