Trim the lamb loin of all fat, then cut it into pieces across the loin around 1.5cm (½") thick and place them in a bowl.
Peel and mash the garlic cloves and add to the bowl.
Add the grated ginger to the bowl.
Pour in the yoghurt and then all the spices, herbs and salt.
Mix well, cover with cling film and then place it in the fridge to marinate for at least 4 hours and up to 24 hours.
If you use bamboo skewers, soak them for 30 minutes before creating the kebabs.
Top and tail the onion, peel it, cut it into quarters, and then separate it into individual onion leaves.
De-seed the green pepper and then cut it into 1.25-2cm (½-¾") dice.
Thread the lamb onto the kebabs, alternating pieces of lamb with onion and green pepper.
Place under a preheated grill or broiler as hot as you can get it, then cook until the kebabs are nicely coloured, which will take 4-5 minutes per side.