Beat together the ketchup, water, black treacle, Worcestershire sauce, white wine vinegar, Dijon mustard, light brown soft sugar, salt, hot pepper sauce, garlic granules and black pepper together in a small heavy-bottomed saucepan and place over medium heat.
Bring to the boil, reduce heat to low and continue cooking at a simmer, stirring together, another 10 minutes. Remove from heat and allow to cool completely. Pour into a glass jar and store uncovered in the refrigerator for 8 hours or overnight. This allows the flavours to blend and reduce any sharpness from the vinegar.