Cover the lentils with plenty of cold water, add the bay leaf (and the stems from the parsley, if you like) and bring to the boil. Boil for a minute or two then drain. Discard the bay leaf.

Put the lentils back in the pan and add water to cover them but only by ½in/1cm. Bring back to boiling and simmer for around 25min. They should be tender but not going mushy. Top up water if needed as they cook so they don't dry out. It's better to have too much and drain than have them stick.

While the lentils are cooking, add the 1tbsp oil to a skillet/frying pan over a medium heat. Slice the celery and fennel, cutting larger slices into smaller chunks, then add to the pan. Cook for around 5min or more until tender and just starting to brown then set aside.

When the lentils are cooked, add the 2tbsp oil, vinegar and salt and pepper and mix well, being careful not to break the lentils.

Break up or dice the feta and roughly chop the parsley leaves. Add both plus the fennel and celery to the lentils. Mix through and serve either warm or at room temperature.