A man has been arrested on suspicion of murdering a police officer who was shot dead at Croydon custody centre.
New Zealand-born Sgt Matt Ratana, 54, died after he was shot in the chest as a handcuffed suspect was being taken into custody on 25 September.
Louis De Zoysa, 23, also suffered a gunshot wound and was taken to hospital in a critical condition.
The Met Police said he has since improved and was considered fit to be arrested on Friday.
Mr De Zoysa remains in hospital and detectives will consult with doctors and legal advisers before they begin interviewing him.