Gentleman's Relish is a type of anchovy paste. It is also known as Patum Peperium.
It was created in 1828 by an Englishman called John Osborn. It has a strong, very salty and slightly fishy taste, and contains anchovies (minimum 60%), butter, herbs and spices. Today, the secret recipe is withheld from all but one employee at Elsenham Quality Foods in Elsenham, England, the licensed manufacturer.