Heat olive oil in a heavy-based pot over medium-high heat. Season the lamb lightly with salt, then brown in batches for 3–4 minutes per side until well coloured. Remove and set aside.
Reduce heat to medium. Add onion and cook for 6–8 minutes until soft and lightly golden. Add garlic, tomato paste, allspice and cinnamon and cook for 1–2 minutes, stirring constantly.
Return the lamb to the pot. Add crushed tomatoes and water or chicken stock. Stir, scraping the bottom of the pot. Bring to a gentle simmer, cover and cook on low heat for 2 to 2½ hours, or until the lamb is very tender and can be easily broken apart with a spoon. If still firm, continue cooking and check every 20 minutes.
Using a small knife, trim around the stem of each okra to remove the tough top, without cutting into the pod or slicing it open.
Heat a frying pan over medium-high heat with a little olive oil. Add okra in a single layer and cook for 5–8 minutes until lightly browned, turning occasionally.
Once the lamb is tender, add the okra to the pot. Simmer uncovered for 20–30 minutes until the okra is tender and the sauce has thickened slightly. Stir gently.
In a small pan, heat olive oil over medium heat. Add garlic and cook for 20–30 seconds (do not brown). Add coriander and cook for 1–2 minutes, stirring.
Stir the garlic and coriander mixture into the stew. Add lemon juice to taste, starting with half a lemon. Adjust seasoning and serve hot.