And what a shocker that 2005 defeat was as Posh went down to non-league Burton Albion 1-0 in a replay.
The teams had drawn the first game 0-0 at London Road.
Mark Wright was the Posh manager at the time with his old Liverpool teammate Nigel Clough in charge at Burton.
The result put travelling Posh fans in a foul mood.
Wright wasn’t best pleased either. He came out to see the press at 11pm.
1. LAST SHOCK
Posh don't have to travel too far back for their last FA Cup defeat against lower level opponents. In the 2020-21 season non-league Chorley came from behind to win 2-1 at London Road, although Posh did go on to win promotion to the Championship. Jonson Clarke-Harris was the only regular Posh starter not to feature against Chorley and he could be absent against Salford tomorrow. Photo: David Lowndes
2. UNIQUE EXPERIENCE
Posh beat Kingstonian 9-1 in a first round replay in 1992, but the game was declared null and void after a coin thrown from the London Road End struck the visiting goalkeeper. That was hard luck on Tony Philliskirk (pictured) who scored what would have been a record five goals in a record margin of victory, in the club's Football League era. Posh played the game again in front of no fans and won 1-0. It's officially the lowest home gate in Posh history! Photo: DAVID LOWNDES
3. LOWEST GATE
The lowest FA Cup gate at London Road (when fans were allowed in) is the 2,312 which saw Posh beat Stockport County 4-1 in a first round replay. Craig Mackail-Smith (pictured), Lee Tomlin, Aaron Mclean and Kelvin Langmead scored the goals. Photo: David Lowndes
4. BIGGEST UPSET
Arsenal are the only top-flight team Posh have ever beaten in the FA Cup. Goals from Derek Dougan and Peter McNamee secured a come-from-behind 2-1 win at London Road in a fourth round tie in 1965, Photo: David Lowndes