"For a girl with no sense of direction, poetry was a route map through life," explained Josephine Hart. Guiding us with grace and good humour through the mysterious inner workings of some of the greatest ever poems are Hart's wonderful introductions here collected, initially given at her popular public events at which leading actors brought poetry alive in the spoken word, the legacy living on in the Josephine Hart poetry hour at the British Library.

Why do we need poetry? This joyous, vital volume captures centuries of life-affirming wisdom. A poem is "a momentary stay against confusion", declared Robert Frost, who "carved grace out of tragedy". Art can help us to "enjoy or endure", believed Larkin. Poets are, asserted Shelley, "the unacknowledged legislators of the world". Hart herself was deeply aware from childhood that "poetry startles us into a more full sense of life".

That language can grow out of loss is elucidated as Hart sensitively traces a poem's gestation, revealing how many great poets had "tough beginnings" in which poetry provided essential nourishment. "If an unhappy childhood is a great gift to a writer, then Kipling was truly blessed", is just one example.

The "metaphoric power of the garden" is the subject of part II, its budding and withering reflecting life's natural rhythms, assuring that when what was loved has been lost, hope remains; as Larkin wrote in The Trees, we may "begin afresh, afresh, afresh".

A moving afterword by Hart's husband Maurice Saatchi serves as an introduction to Hart herself, who died in 2011. Aged 13, Hart was awarded a Royal Life Saving Institution Certificate "for the ability to render aid in resuscitating the apparently drowned"  this fine collection shows how poetry too can cast a life-raft, helping us to swim not sink.