JayDee Custom Guitars was founded in Birmingham, England in 1977 by luthier John Diggins, whose nickname "Jay Dee" gave the company its name. Having apprenticed under fellow Birmingham luthier John Birch, Diggins established his own workshop and quickly built a reputation for exceptional handmade instruments. The shop gained early recognition crafting and repairing guitars and basses for a notable clientele that included Tony Iommi and Geezer Butler of Black Sabbath, Noddy Holder of Slade, Angus Young of AC/DC, and Roy Orbison.

The brand's most iconic creation is the Supernatural bass, developed in collaboration with Mark King of Level 42. Featuring custom hand-wound, wooden-cased pickups with active electronics, the Supernatural helped define the slap bass sound of the 1980s and remains the cornerstone of JayDee's catalog. Diggins also built "The Old Boy," a custom SG-style guitar for Tony Iommi that became Iommi's primary instrument for both studio recordings and live performances, pioneering features such as locking nuts that later became industry standard. JayDee was additionally responsible for building the first authorized replica of Brian May's Red Special.

JayDee Custom Guitars remains a family business based in Birmingham. Following John Diggins' passing in January 2024, the workshop continues under the stewardship of his wife Helen, sons Michael and Andrew, and grandson Toby. All instruments are built to order by hand, with the range encompassing custom electric guitars, basses, and hand-wound pickups.

JayDee Custom Guitars has 13 products cataloged on Equipboard, including Solid Body Electric Guitars, Electric Basses, and Fretless Basses. Their gear is featured by 9 artists, with the strongest followings in Rock, Jazz, and Funk / Soul. Notable users include Tony Iommi, Geezer Butler, and Mark King Level 42.