Two men were stabbed and had to be taken to hospital after a incident in Beddington Park yesterday.
Police and paramedics were called to reports of stabbings near Church Road at 6.42pm.
Several ambulances attended including London's air ambulance.
One person was flown to hospital for urgent treatment and another was driven to a different hospital as a priority.
One of the men, aged 26, suffered wounds to his neck and chest, the other, 21-years-old, had wounds on his chest.
The injuries are believed to have happened after a fight broke out between two families at the park.
One man, aged 31, was arrested on suspicion of GBH and is being treated for injuries in hospital. Another, aged 32, was arrested on suspicion of violent disorder and remains in custody.
Police are appealing for information. If you can help call 101 or the charity Crimestoppers on 0800 555 111.
Do you know more? Contact reporter Mike Murphy-Pyle on 020 8722 6359 or email firstname.lastname@example.org.