I'm sorry but at 3 1/2 years old you watch them all the time and don't slack off!

Having said that my 13 year old was an escape artist at that age and could regularly be found at 4am sitting in the neighbours jeep. So I do sympathise.

If nanny is leaving your child alone in a car its nanny that needs speaking to not your child.

Put extra locks on the doors, remove all items that could be used to help him reach them, alarms are an excellent suggestion, (where where you 10 years ago Liz ) may not stop him escaping but at least you'll know he has.

Afraid telling him what might happen will have no effect and quite possibly encourage him to test the theory out. Just put as many barriers in his way as possible, the idea is to buy time for yourself to realise what he's up to.