A brave bystander leapt into action when a blazing bus pulled up next to him.

Colin Baines, of Newport Pagnell, was waiting for his wife outside Waitrose on Midsummer Boulevard on Saturday afternoon when he smelled burning – then heard an explosion.

The 49-year-old sprung into action using the fire training he learned with his security firm as he saw a No 8 Metro bus on fire.

Colin said: "Flames were coming from underneath and I shouted to the driver to get the passengers off.

"Quick as a flash I ran into Waitrose and grabbed several fire extinguishers.

"The fire had taken hold of the electrical system, burst the air suspension and fuel tank and was squirting fuel from the tank on to the fire.

"Had I not been able to get there the whole back of the bus would have been totally engulfed in flames."

No one was injured in the blaze with firefighters arriving soon after.

But Colin said he was stunned by the lack of help he received as he was left to extinguish the huge flames single-handed. He said: "A crowd gathered but instead of anyone helping they just watched.

"A security guard from thecentre:mk came running up and down the road shouting 'get back, she's about to blow' like something from a Hollywood film!"

A spokesman for MK Metro said it is not yet known what caused the fire.

A statement said: "MK Metro can confirm that a bus on route eight travelling towards Westcroft caught fire on Saturday afternoon.

"The bus was in service and the fire brigade attended. No one was harmed and the driver and passengers were uninjured.