Measure the reserved liquid from the salmon and top up with water to make 125ml. Place into a pot and sprinkle the gelatine on top. Heat gently until the gelatine is completely dissolved, stirring frequently. Let cool.
Put the salmon, gelatine liquid, Worcestershire sauce, onion, mayonnaise, lemon juice and seasonings into a liquidiser. Blend until smooth. Adjust seasonings, if necessary.
Pour the mixture into moulds or a cling film lined loaf tin and refrigerate. Chill until set, then serve.