Soused herring with heritage potato, celery salad and bloody mary sauce

Name: Soused herring with heritage potato, celery salad and bloody mary sauce
Cook time: 2 h 30 min
Total time: 2 h 30 min
Cuisine: European, British
Ingredients: 6 herring, filleted and trimmed; 500ml of water; 90g of table salt; 600ml of white wine vinegar; 200g of caster sugar; 250g of onion, peeled and sliced; 1 bay leaf; 10 black peppercorns, crushed; 2 allspice berries, crushed; 1 sprig of thyme; 125ml of tomato essence; 1 tbsp of Worcestershire sauce; 1/2 lemon, juiced; 1/4 tsp flaky sea salt; black pepper, freshly ground; 7g of horseradish, grated; 25ml of rapeseed oil; 500g of pink fir apple potatoes; 4 celery sticks; 3 tomatoes