"Cranbrook", also known as "Northampton", is a hymn tune composed in the 1790s or early 1800s by Thomas Clark (1775–1859), a cobbler from 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.
In order to fit, the third line is sung twice and the fourth three times as in "Grace 'tis a charming sound", "While Shepherds Watched Their Flocks" and "On Ilkla Moor baht 'at".
Thomas Clark was a regular visitor to Cranbrook, Kent in the 1790s, and may have composed the tune there, possibly with the help of a local schoolmaster, John Francis.
Clark later became a choirmaster and composed many other tunes for churches and Sunday Schools.