Heat the oil in a large saucepan over a medium heat. Add the onion, celery, courgette, and carrot. Season with salt and pepper and cook over a low heat for 10 minutes. Stir with a wooden spoon until the vegetables are soft but not brown.
Add the garlic and herbs and cook for a minute or two before adding the potatoes and chickpeas. Stir and cook for a further 5 minutes.
Pour in the hot vegetable stock. Bring to a boil, reduce the heat and simmer for 10 minutes or until the potatoes are soft whilst still retaining their shape.
Using a ladle, take two spoonfuls of the soup and blend until smooth before returning it to the saucepan.
Add the spinach and cook until wilted and add a squeeze of lemon juice.
Taste the soup, adjusting the seasoning if necessary.
Spoon into warmed bowls, garnish with a slice of lemon and serve with crusty bread.