With police approval, you can now leave a spare front door key outside your house. But leaving it under a flowerpot or a mat in case of emergencies or forgetfulness is not recommended for obvious reasons. Nor is hanging it on a string inside the letterbox!
Leaving a key with neighbours is better if you can trust them and if they will be there when the key is needed.
However, you can now can now leave a spare key outside with total confidence by fitting a C500 KeySafe™ - just announced by Supra UK Limited...