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The manufacturer Alcolock says some bus and lorry fleets already have the gadgets fitted and suggests that parents of young drivers should consider installing it too. 's Stephen Chittenden tried it out.

The way the alcolock works is that the driver must first breathe into it to unlock the engine, and will have to repeat the same process at regular intervals during the journey.

But now company vehicles come equipped with an Alcolock, a device drivers must blow into before turning on the ignition.