Police have arrested a 36-year-old man on suspicion of GBH following an incident at the junction of Great Russell Street and Museum Street around 10am on Tuesday 8 August.
A 36-year-old man was treated for a stab wound to the arm at the scene and taken by London Ambulance Service to hospital.
His condition was later assessed as not life-threatening or life-changing.
This was an isolated incident and there is no outstanding risk to the public. It is not being treated as terror-related.
The scene may be in place for much of today.
Anyone with information or footage which could assist the police investigation is asked to contact police on 101, quoting CAD 2184/08AUG, or anonymously via Crimestoppers on 0800 555 111.