The officers discovered the man had been stabbed.
A police cordon was put up close to the Quin’s Bar and forensic officers have been at the scene.
A 22-year-old man has been arrested on suspicion of GBH and remains at Thorpe Wood Police Station.
Anyone with information about the attack should contact Peterborough CID on 101.
The man was taken to hospital with serious but not life threatening injuries and is in a stable condition.
Officers on patrol in Whittlesey during the festival received reports at 3.35pm yesterday, Saturday January 13, that a man had been assaulted in Market Street.