Preheat the oven to 200C/400F/Gas 6.
For the sea bass, place the fish on a baking sheet and rub the slashed flesh and insides of the fish with salt and freshly ground black pepper. Stuff the inside and slashed flesh with a handful of mixed chopped herbs.
Drizzle with olive oil. Squeeze the juice of one half of a lime over the fish and place the other 3 pieces around the fish on a baking tray.
Place into the oven to roast for 20-25 minutes, until cooked through.
For the sweet and sour rhubarb, melt the butter in a saucepan until bubbling. Add all of the other rhubarb chutney ingredients, stir and cook on a medium heat for 8-10 minutes, or until the rhubarb has softened and the sauce is thickened.
For the leeks, melt the butter in a frying pan over a medium heat. Add the chopped leeks and sauté until cooked through and lightly browned on all sides. Season with salt and freshly ground black pepper.
For the spinach, melt the butter in a wok or large pan over a medium heat. Add the spinach and cover with a lid for 30 seconds. Remove the lid and toss the spinach thoroughly. Replace the lid and cook for a further 30 seconds, until the spinach has wilted down. Remove from the heat, drain of excess liquid and season with salt and freshly ground black pepper.
To serve, place the spinach on a large oval plate and place the sautéed leeks around the spinach. Place the sea bass on top of the leeks with the roasted limes round the side of the plate. Serve with the sweet and sour rhubarb chutney in a small dish on the side.