Difficult though it may be, you have to detach yourself from a question so bound to provoke emotions - protectiveness; anxiety about your child's popularity; resentment at the parent for so callously leaving Eddie off the invite list. All these will be magnified if Charlie is a particularly close friend. First, try to look for practical reasons why he didn't get the call.

Helen Cowie, a professor of child development psychology, takes an optimistic view: “Maybe you've misconstrued it and the number had to be limited.”

Annie Mitchell, an educational psychologist, says: “I would reflect the question back on the child. Ask why he or she thinks they weren't invited; did they do something to upset them?” If there's something else going on, the parent needs to find out. Has this friend turned against him? Could it be a form of bullying? Chances are this isn't the case, but this needs to be ruled out.

As well as you feeling slighted on your child's behalf, it can feel like a personal rejection, too, especially if you know Charlie's mother. “At this point, you need to step back and think, this is about your child and not you,” says Mitchell. Cowie agrees. “There is a danger that parents can be very competitive about who's invited where.” Of course, it is only natural that you want your child to be popular and included, and to get along with mothers yourself.

Ask your father: why wasn't I invited to his party?

What to say to your child when they are passed over for an invitation to a birthday party

BACKGROUND

• Ask your father: Mummy, can I have a toy gun?

• Ask your father: Why did Daddy say a bad word?

• Ask your father: why do some people have white skin?

• Ask your father: can you fly to heaven?

• Why doesn't Jack's dad live with him?

In this case, if Eddie is keen on Charlie, maybe you could take a more proactive stance. “Another way to get invited next time is to have a party yourself,” says Cowie. “Don't wait to be included. Ask them for tea or organise a picnic, but don't sit at home feeling rejected.” This applies equally to parent and child.

In fact, your child could be asking the question more out of curiosity than wounded disappointment. He will, however, be aware of your response, so try to be upbeat and breezy. “Say something like, 'You don't always get the invite you want; not everyone can go to one party, but don't worry, there'll be plenty of other invites in the future',” says Cowie. And, if you are thinking that's the last time I bother making small talk with Charlie's mum at the pool, just keep it to yourself.

Times recommends

• What took place in 2010...
• Can you really cure a hangover?
• Video: How to do glamorous smoky eyes