Amy Winehouse checked back into her London clinic after a chaotic appearance at the Glastonbury Festival during which she attacked a crowd member.
The 24-year-old singer climbed down to the pit in front of the stage to meet fans during set closer 'Rehab', and scuffled with an unseen reveller, reports the Sun.
The crowd had lapped up hits, including 'Back To Black,' although there were jeers when Winehouse dedicated 'Wake Up Alone' to husband Blake Fielder-Civil, in jail awaiting sentencing for GBH and perverting the course of justice.
The singer could not resist pining for her imprisoned husband and punched a crowd member hard in face.
Festival boss Michael Eavis said of the singer's punch: "The man deserved it. He grabbed Amy's breasts as she went past."
Winehouse spokesman said: "One person misbehaving did nothing to spoil a great couple of days."
However, another crowd member in the front row, said it was a girl who was hit, after trying to give the singer a high-five.
Avon and Somerset Police received no complaints and said that there would be no investigation.