It's Friday night, you feel fine, but you know the limit is two drinks, and you can't remember the precise number of glasses you've had. There is always the danger of being breathalysed on the way home. Should you risk it? What are you, mental? They'll take away your licence and you'll be branded a criminal! The sensible thing to do is to leave your car outside for the clampers at dawn and go and stand in the rain at the taxi rank for three hours. But wait . . . now there is an alternative. Simply drive home anyway, and if a garda stops you, roll down your window and address him or her sternly with these words: "Guard, stand up straight. Have you been drinking? I'm going to have to ask you to blow into this keyring."

The officer should then blow into the Breathalyser Keyring, whereupon you should examine it and state: "Hmm, inconclusive. I'll let you off with a warning." On the other hand, you could use the keyring to test your own breath before you leave the pub, and keep blowing into it as you wait in the taxi queue until it's safe for you to leave and drive home. The Breathalyser Keyring, around £35 (€44), is available from www.boysstuff.co.uk and other top gizmo stockists.