Martin Miller's Westbourne Gin is produced in England using two separate distillations: the first macerates earthy, spicy botanicals — Tuscan juniper, cassia bark, clove, nutmeg, angelica, orris root, and liquorice — in wheat-based neutral spirit before distillation; the second distils only the delicate citrus botanicals — Seville orange peel and lemon peel — to preserve their brightness. The two distillates are then blended with a cucumber distillate and combined before being shipped to Iceland, where Icelandic spring water of exceptional purity is used to reduce the spirit to 45.2% ABV for the Westbourne Strength expression.

Martin Miller's Gin is produced through a distinctive two-stage process: the botanical distillation takes place in England using Angela, a copper pot still built in 1904 by John Dore and Sons in Birmingham, before the spirit is shipped to Borgarnes, Iceland, where it is blended to strength using Icelandic spring water — water sourced from snowfall over 800 years old, naturally demineralised through filtration over volcanic rock. The Westbourne Strength expression is the higher-proof version of the flagship Martin Miller's gin, bottled at 45.2% ABV. The brand takes its name from founder Martin Miller, a British antiques dealer and author who developed the recipe in collaboration with a distillery team in the late 1990s.