Martyn Waghorn scored a hat-trick as Derby came from behind to claim victory.
Match photographer David Lowndes captured some of the fans in the stands in this gallery.
Take a look and see if you can spot a familiar face.
Get all your latest Posh news, here.
Take a look and see if you can spot a familiar face.
![Peterborough United fans watch their side's defeat to Derby County.](https://www.peterboroughtoday.co.uk/webimg/b25lY21zOmUzYzgwZDM0LTk1ODYtNGM4OC1hOGFhLTNmYmM0NjE4YzA5MjpjNDAwODc0Ny1hOWJlLTQ4OGYtYTFiMy0zMjRlYjY5YjY2Yjk=.jpg?crop=3:2&width=800)
41. Posh 2 Derby 4
Peterborough United fans watch their side's defeat to Derby County. Photo: David Lowndes
![Peterborough United fans watch their side's defeat to Derby County.](https://www.peterboroughtoday.co.uk/webimg/b25lY21zOjBkYTg2ZDUwLTIyYTQtNGEzMy04YmJjLTAyYjQxNTM3NDlhZTphMzY3NGJlNS0yNGVjLTQ0YzktYTNlNy1mZmYzNDk2MDc5NmE=.jpg?crop=3:2&width=800)
42. Posh 2 Derby 4
Peterborough United fans watch their side's defeat to Derby County. Photo: David Lowndes
![Peterborough United fans watch their side's defeat to Derby County.](https://www.peterboroughtoday.co.uk/webimg/b25lY21zOjYxN2NiM2NlLTE0OTctNDdiNi05ZDViLTJmMDNjMjYyYmY3YjplMmFmODUwZC03MWIzLTQ3ZTgtOGE3MS0wOGEwZGVmZjczMTc=.jpg?crop=3:2&width=800)
43. Posh 2 Derby 4
Peterborough United fans watch their side's defeat to Derby County. Photo: David Lowndes