Under a small hill in Scotland lives the Swan Clan of fairies. They are constantly at war with the Seal fairies who live out in the bay under the sea. One day a new Swan fairy is born and at her naming ceremony the Black swam from Australia gives her the gift of not being able to tell a lie. Because of this calamity she has few friends among the fairies who are much given to teasing and pretence.
Used availability for Naomi Mitchison's The Fairy who Couldn't Tell a Lie