Pompey surrendered top spot in League One after being held to a 2-2 draw by Wycombe Wanderers at Fratton Park.
Substitute Brett Pitman thought he’d snatched all three points for the Blues with a header on 87 minutes, but Joe Jacobson’s 89th-minute penalty demoted the hosts to second in the table, with Peterborough going to the summit.
Gareth Evans had equalised for the hosts early in the second half after Bryn Morris' 21st-minute opener.
However, Kenny Jackett’s side still remain unbeaten in the league this season after nine games - matching the record set by Harry Reddknapp's Pompey in the 2002-03 Division One campaign.
Following a close start, it was the visitors who made the breakthrough on 21 minutes through a superb goal.
Morris played a one-two with Adebayo Akinfenwa, before bending a right-footed shot from 20 yards beyond keeper Craig MacGillivray.
That gave the Blues a wake-up call after a ponderous start, although they struggled to create many goalscoring chances.
Pompey’s best opportunity of the half fell to Tom Naylor two minutes before the break.
Jamal Lowe cut a ball back from the byline to the midfielder, but he scuffed his close-range shot and visiting keeper Ryan Allsop saved with his legs.
Following a sluggish start to the second period, it took a moment of brilliance from Jamal Lowe to conjure up the Blues’ equaliser.
The winger’s inch-perfect cross from the right picked out Evans inside the six-yard box and he headed home.
Akinfenwa had a gilt-edged opportunity to regain the Chairboys’ lead in the 66th minute, but he headed Morris’ cross wide from close range.
Pompey almost punished that mistake when Lowe burst through Wycombe’s rearguard a minute later – yet his effort was stopped by Allsop.
With a point looking likely, Pitman had different ideas with four minutes left.
Lowe was again the architect, clipping in a wonderful ball for the skipper to head home and give the hosts the lead.
But the Fratton faithful’s celebrations were brief as there was more late drama.
Christian Burgess nudged Fred Onyedinma inside the box to concede a penalty, with Jacobson equalising from the spot and earning Gareth Ainsworth's side a draw.
With Peterborough winning at Gillingham, it means they leapfrog Kenny Jackett's side in the table.
But Pompey are still to suffer a League One defeat this term.