A bus carrying festival-goers home from Victorious burst in to flames late last night.
The double-decker was packed full of passengers who had just watched The Libertines close a very wet first day of the top music event on Southsea Common.
It was on the M275 heading back to the park and ride at Lakeside when passengers on the top deck said they could feel the bus heating up.
Within seconds flames could be seen coming from the grill behind the back seat sparking an initial scramble to reach the stairs and the safety of the lower deck.
The bus immediately pulled over on to the hard shoulder and, after the initial confusion over what was happening, calm was restored and the driver ensured everybody was off safely.
As passengers waited on the hard shoulder the bus could be seen filling with smoke and thick white plumes continued to pour from the roof.
It was not long before the smoke turned to flames which shot from the top and the back of the bus as the fire started to take hold.
Emergency services were quickly on the scene and closed off the northbound carriageway, near the Sails of the South, while two fire crews doused the flames.
A replacement bus was called and the passengers, who had spent 20 minutes in the cold and wet behind the safety barriers as the drama unfolded, were taken on to their journey back to Lakeside and on to the Victorious campsite at Farlington.
Mark Waldron, editor of The News, Portsmouth's daily newspaper, was one of the passengers on the top deck.
He said: "It was a very dramatic end to what had been a enjoyable opening to Victorious.
"There was initial confusion and panic as those at the back of the bus rushed to the stairs while those at the front were unaware of the drama happening behind them.
"But once the cause was known, the bus pulled over and we all filed out to safety behind the crash barriers on the hard shoulder, It was quite a spectacle as the flames took hold but the firefighters were quickly on the scene and the fire was instantly out.
"Watching as the bus caught alight you were just left feeling incredibly thankful that nobody was injured."