Gardiner comes from a family of English intellectuals. His grandfather was an Egyptologist, his father a forerunner of organic farming and his grandfather's brother a composer. The Australian composer Percy Grainger was a  classmate of his great-uncle and Gardiner met Grainger when he was a young boy—but Gardiner's lifelong affiliation with another composer is even more fascinating.

A famous portrait of J.S. Bach painted by 18th-century German painter Elias Haussmann was hung in Gardiner's house when he was young. It was entrusted to the family by its owner for safekeeping during World War Two and Gardiner was instrumental in the return of the portrait to Germany in 2015. Gardiner recalls looking at the painting every day until he was 10 and it's worth exploring how being under the gaze of the great Baroque composer contributed to his becoming a Bach aficionado.

In 2000, to mark the 250th anniversary of the death of the composer, Gardiner set in motion the Bach Cantata Pilgrimage. Along with the English Baroque Soloists, he directed the Monteverdi choir to perform 198 of Bach's sacred cantatas in 63 churches, and had the long list of performances recorded and released. In 2018, to celebrate the 333rd anniversary of Bach's birthday, Deutsche Grammophon released a mega box set of 222 CDs, including a foreword by Gardiner.