And they were made to pay when JulioArca picked out Emnes' run through the middle and the Dutchman calmly tucked his shot inside Simonsen's far post to move Boro 11 points clear of the relegation zone.
The Posh keeper was increasingly involved and although he stopped a strike from JulioArca, the England Under-21 stopper could not prevent Kitson from slotting home the rebound as Middlesbrough took the lead just after the half-hour mark.