It took place at an address in Hudson Road at around 5.15am on Sunday 3 February. A 21-year-old man sustained a gunshot wound to his leg.
The young man continues to receive treatment at hospital and remains in a stable condition.
On Wednesday 13 February, a 20-year-old man from London was arrested on suspicion of attempted murder.
He has been released from custody but remains under investigation.
It follows the arrests of a 24-year-old man, a 25-year-old man and a 21-year-old man, all from the London area.
They were all arrested on suspicion of attempted murder. They were released from custody but remain under investigation
Chief Inspector Rob Mitchell said: “Our detectives are working hard to find out exactly what happened that morning.
“We would like to reiterate that we believe this was an isolated incident with no wider risk to the community.
“However, if you have any concerns, or if you have any information about what happened that you have not yet shared with us, then please call 101, quoting Operation Lament/44190040783.
“You can also call Crimestoppers on 0800 555 111, where information can be left anonymously.”