A 20-year-old man was arrested on suspicion of murder on Friday, 9 October. He was taken to a south London police station where he remains in custody.
Police were called at 10.57pm on Thursday, 1 October to reports of a stabbing outside a block of flats on London Road in Morden.
Officers and the London Ambulance Service attended. Two men were found with stab wounds.
Despite the best efforts of paramedics, 25-year-old Patrick Gomes De’Almeida was pronounced dead at the scene at 11.26pm
A second man, aged 33, was taken to hospital. His injuries were not life-threatening.
Detectives are continuing to appeal for anyone with information or who saw what happened to come forward and speak with them. They are asked to call police via 101 quoting reference Cad 7953/01Oct.
Alternatively, to remain anonymous call Crimestoppers on 0800 555 111.
Two men have previously been charged with Patrick’s murder.