Amy Winehouse joined Pete Doherty on stage during his performance on the Union stage at the V Festival this weekend.
She appeared in the wings mid-set before running on stage and kissing Doherty, then running and hiding behind a drum.
Security guards appeared to ask Winehouse to move, but she remained on stage until Doherty dedicated a song to her, when she emerged at the front of the stage.
Winehouse grabbed the microphone and called to the crowd repeatedly: "Ladies and gentlemen, Mr Peter Doherty."
Towards the end of the set she kissed Doherty on the mouth and shortly afterwards they ran off stage together arm-in-arm.
Winehouse earlier made her return to live performing by appearing on stage at the festival with Ska legends The Specials.
She performed 'You're Wondering Now' and sang backing vocals on 'Ghost Town'.
A spokesman for the singer said: "While living in St Lucia, Amy missed the band's reunion tour and decided to head to V to catch her favourite artists.
"Meeting them backstage, they invited her to guest for them and made her dream come true."
Before leaving the stage, Winehouse thanked the band and urged the crowd to pay their respects.
Brit rockers Oasis will help bring the V Festival to a close today.
The Manchester band headlined the festival's Weston Park venue in Staffordshire last night, and switch to the twin site in Hylands Park, Chelmsford, tonight.
Fans will be hoping the occasionally volatile relationship between the Gallagher brothers holds for another day at least after Noel and Liam recently revealed they are not speaking to each other.
Thousands of festival-goers have been partying at both sites since Friday night, enjoying performances from the likes of The Killers, Lily Allen, Katy Perry and Lady Gaga.
Also on the roster are The Specials, Elbow and Dizzee Rascal. Artists play each venue over the weekend.
Yesterday, newly-converted cricket fan Lily Allen asked fans for the score from the final Ashes Test.
She has enjoyed several days of play the The Brit Oval before arriving in Chelmsford for her set.
The 24-year-old singer wore denim hot-pants, a revealing black vest and towering black stilettos to show off her tan and figure, telling festival goers: "Hello England, it's good to see you lot."
Elsewhere at the festival, Jade Goody's widower Jack Tweed was spotted enjoying the hospitality bar in the Absolute VIP area with a group of male friends.
TV presenter Myleene Klass was also seen dancing with her two year-old daughter Ava in the Virgin Media Louder Lounge VIP Area, while Doctor Who star Billie Piper and husband Laurence Fox had left nine month-old son Winston at home to come and enjoy the festival.