Crab Cocktail with Pickled Cucumber

For the cucumber

1 cucumber

150ml apple cider vinegar

150g caster sugar

75ml water

1 tsp sea salt

For the crab

50g picked white crab meat

1.5 tbsp mayonnaise

1 tbsp crème fraiche

1 tbsp ketchup

1 tsp Dijon mustard

1 tsp hot sauce

Juice of one lemon, zest of half

4 baby gem lettuces

2 tbsp olive oil

2 sprigs of dill

¼ tsp smoked paprika