When somebody stands up to the playground bully the bully usually backs down. This is because most bullies are cowards and whilst they like to dish it out they don’t like getting it back. However, it’s no use threatening the bully unless you intend to carry out that threat.

The same thing applies when dealing with children, as any responsible parent or competent teacher will testify. If a child is warned of the consequences of bad behaviour and no consequences follow his bad behaviour he will know that the warnings are meaningless and he will continue to behave badly.

I wonder if Putin would behave the way he does if he was faced by a Kennedy or a Reagan?