A man has been arrested on suspicion of inciting racial hatred after allegedly posting a tweet in response to the Brussels attacks.
The tweet read: "I confronted a Muslim woman yesterday in Croydon. I asked her to explain Brussels. She said 'Nothing to do with me'. A mealy mouthed reply."
Matthew Doyle, 46, was arrested on Wednesday night in Croydon.
He remains in custody at a south London police station, according to a spokesman for the Met.
Police would not confirm whether the arrest relates to the tweet which went viral or to other statements on social media posted by the same user.
At least 31 people were killed and scores injured when bombs went off in the Belgian capital on Tuesday.