Nabbed this off of the Beeb cookery site:

Quick tartare sauce

Ingredients
200ml/7fl oz mayonnaise
3 tbsp capers, drained and chopped
3 tbsp gherkins, drained and chopped
1 small shallot, finely chopped
squeeze of lemon juice
3 tbsp chopped fresh parsley
flaked sea salt and freshly ground black pepper

Preparation method
Mix together all of the ingredients in a small bowl and serve straight away or store in the fridge until needed.