Site managers said "something like a whirlwind" had caused the incident at the airfield site, at about 12.40pm on Saturday.

Two land vehicles and the Warwickshire and Northamptonshire Air Ambulance rushed to the scene. A spokesman said: "The exact details of what happened were not clear, but people said a metal pole suddenly came off a market stand and hit the patient who was standing some distance away.

"He was struck on the back and sustained upper back and shoulder injuries and was in considerable pain.

"Crews say that had it been a child, the situation might have been very different."

Market organiser Gary Platt said the injury had been caused by a sudden gust of wind.

He said: "We had something like a mini whirlwind and one of the poles was blown out. In the end it wasn't a real emergency and the chap came back to get his car himself about an hour-and-a-half later."

The man, in his 40s and from Gloucestershire, was taken to Warwick Hospital and treated for bruising.

Meteorological Office forecaster Kevin Hogg said no tornadoes or 'dust devils' had been reported in the area on Saturday, although there were reports of problems with flying debris at a market on an airfield site in Essex.

Mr Hogg said: "It wasn't the kind of day in which we would have tornadoes reported - there's no chance - although it was very windy."