Preheat your oven to 200°C/Fan 180°C/Gas 6. Trim the base and woody tips off the fennel. Halve the fennel and slice into 1cm-thick pieces. Spread out on a baking tray, drizzle with 1 tbsp olive oil, season with a pinch of salt and pepper and toss to coat. Slide the fennel into the oven and roast for 25 mins, till tender and caramelised.
Meanwhile, grate the lemon zest into a bowl and squeeze in the juice. Rinse 1 tbsp capers under a cold tap and add them to the bowl. Peel and grate in the garlic. Pour in 1 tbsp olive oil and add a pinch of salt and pepper. Roughly chop most of the oregano leaves. Add the chopped oregano to the bowl. Stir to make a dressing and set aside.
Drain and rinse the chickpeas with cold water. Shake dry and tip into a large bowl. Halve the cherry tomatoes and add them to the chickpeas.
When the fennel is cooked, add it to the bowl with the tomatoes and chickpeas. Pour over the dressing. Add the watercress and fold together.
Divide the salad between a couple of plates and serve topped with the remaining oregano leaves.