A ‘wing slide’ advisory message activated on the Engine Indication and Crew Alerting System (EICAS) during takeoff. The crew entered a hold to burn off fuel until the aircraft was at an appropriate landing weight and returned to Gatwick. Whilst positioning for final approach, the right over-wing slide unravelled from the slide carrier and subsequently detached from the aircraft. Although the crew experienced some uncommanded roll on final approach, the aircraft landed safely. The investigation determined that a series of technical issues with the slide panel and carrier locking devices caused the slide carrier to deploy and the slide unravel. A Service Bulletin was already in existence to address some of these issues, but it had not been actioned on this aircraft at the time of the incident. During the course of the investigation, issues were identified on aircraft door designations and the Quick Reference Handbook. Two Safety Recommendations are made.