The crowd went mad as Winehouse jumped out of the audience to sing just two lines with the Before I Die rapper before disappearing again.
One audience member told us: "She came on unexpectedly and the crowd went wild."
They added: "She looked unsteady on her feet and appeared to be nervous."
It is unknown whether the duet was planned, but the Professor himself seemed happy with their brief collaboration later tweeting: "Just tore Camden a new one! Amy Winehouse jumped on stage and sung just be good to green!!"