Bob’s safety awareness clearly leaves much to be desired. Riding around the countryside clinging to the outside of a digger is not generally regarded as good practice.

By contrast former army engineer Glen Stewart is touring the nation telling pupils about the dangers of construction sites - both when buildings are going up and when they are coming down. As more and more 1970s high-rises are being demolished, Glen, now health and safety manager with Controlled Demolition Group, is spreading the word.

He shows pupils clips of imploding buildings and talks them through how the explosion takes the building apart floor-by-floor.Youngsters get a chance to get into character by dressing up in hard hats, goggles, boots and jackets. They are asked to design a poster to keep children off sites where injuries occur every year.

Mr Stewart said: “Buildings being prepared for blow-down may look solid enough from the outside but pre-weakening work makes them very dangerous places to be.”

At Taylor Road school, in Leicester, children celebrated his visit by donning Bob the Builder fancy dress and taking part in a karaoke competition. Headteacher Chris Hassall said: “The tower blocks have been landmarks in the city for 40 years and most children have been inside them. Glen’s visit added to the project we are doing on the buildings and brought home the safety message.”

Julie Henry