A last-minute own goal from Eric Huskelepp gifted Peterborough their first away win of the season at Fratton Park this evening.
Peterborough led twice following a first-half double from Lee Frecklington.
However, Portsmouth fought back, firstly equalising courtesy of a Gabriel Zakuani own goal and then again through Benjani, just short of the hour mark.
Huseklepp was the provider on both occasions, squaring for Benjani to score after previously seeing Zakuani turn his angled shot goalwards.
However, at the other end the Norweigan diverted Ryan Tunnicliffe's effort into his own net five minutes into added time to gift the Posh all three points.