1.Heat oil in the pressure cooker on medium. Saute onion, celery and garlic 1-2 minutes. Add spices and cook 30 seconds, until fragrant.
2.Add hock to pressure cooker with tomatoes, stock, peas and half the thyme. Stir to combine.
3.Close the pressure cooker. Bring up to pressure following manufacturers instructions (until steam escapes at a constant rate and there is a regular hissing sound). Reduce heat to low. Cook for 45 minutes.
4.Release pressure straight away. Remove lid. Remove ham hock and shred meat. Return ham to soup, discarding bone.
5.Serve soup sprinkled with remaining thyme. Accompany with crusty bread.