Amy Winehouse had sex with her husband Blake Fielder-Civil before he was sent back to prison.
Blake - who made a dramatic bid to see his wife on Tuesday night by breaking out of rehab and dashing to see her at The London Clinic - seduced Amy, 25, by telling her how sexy she looked.
He then persuaded carers to allow him and the troubled singer - who collapsed after a drink and drugs binge 10 days ago - to give them some private time.
A source said: "It was obvious what went on - they had a farewell romp."
Earlier that day, Blake had learned he would be returning to prison after failing a drugs test, which meant he broke the terms of his early release from a 27-month sentence for grievous bodily harm and attempting to pervert the course of justice.
A friend said: "Blake turned up in hospital and hell broke loose - everyone was totally shocked. He was asking Amy to forgive him. As he was going back inside anyway he felt he didn't have much to lose."
Following Blake's visit to Amy's bedside he handed himself into police in Shoreditch, East London.
He was originally released into rehab on November 5, but now faces going back to jail possibly until 2010.