Peterborough earned a first win in eight games after beating Walsall 2-1 in front of the man tipped to become their new manager.Caretaker David Oldfield took charge of the success in the heavy ABAX Stadium snow following the Sunday sacking of Grant McCann.Steve Evans - expected to succeed McCann after resigning as Mansfield boss - saw Posh fall behind in the ninth minute when Julien Ngoy raced onto an Erhun Oztumer pass and finished coolly.Posh should have been level within two minutes, but Marcus Maddison saw his penalty saved by the legs of Walsall goalkeeper Liam Roberts after Jack Marriott had been pulled down by Jack Fitzwater.Loan striker Omar Bogle did eventually equalise for the hosts six minutes before the break, pouncing on Nicky Devlin's underhit back-pass to grab his first Peterborough goal.The turnaround was completed eight minutes into the second half when captain Jack Baldwin fired through a crowd of players after Maddison had hit a post.Posh had a lucky escape with 15 minutes to go as Luke Leahy headed an Oztumer corner against a post before Marriott was twice denied a clincher in the closing stages.