Labouring issue???

Was stuck in traffic for around 20 mins yesterday, car got a little hot but nothing unusual, after driving a mile or so down the road after getting outa the traffic, i was in 6 gear and the car seemed to labour even know my foot was still on the pedal, it seemed to loose a little power and feel a little like it was going to cut out, i changed down gear and there was a failry loud bang but it seemed fine, i took it easy for the rest of the journey and nothing happend, was just wondering what this could have been? Any help is appreciated!!!
 
Probaby lost power due to being a little hot, i had these when stuck in traffick on the m40, less power, soon went back to normal as it cooled while driving