"Cranbrook" is a hymn tune composed in the 1790s or early 1800s by Thomas Clark (1775–1859), a cobbler of Canterbury, and is best known as the tune to the Yorkshire "national anthem" "On Ilkla Moor Baht 'at".
The tune was originally published in "A Sett of Psalm & Hymn Tunes with some Select Pieces and an Anthem" in 1805 as a setting for "Grace 'tis a charming sound" by Philip Doddridge, but soon became more widely known as a tune for "While Shepherds Watched Their Flocks" by Nahum Tate. The tune itself is 86.88.666 but is commonly used with lyrics in common metre (86.86). In order to fit the third line is sung twice and the fourth three time as in "Grace 'tis a charming sound", "While Shepherds Watched Their Flocks" and "On Ilkla Moor Bah t'at".
Thomas Clark was a regular visitor to Cranbrook, Kent in the 1790s, and he may have composed the tune there, possibly with the help of a local schoolmaster, John Francis. Clark later went on to become a choirmaster and to compose many other tunes for churches and Sunday Schools.