Drain the olives and but them in a bowl.
Chop the garlic, celery and spring onion ( green parts too). Add these to the olives, together with the dried oregano.
Cut the chilli in half, remove the seeds and the vein. Chop the flesh, add these to the olives (you can use half red bell pepper instead of chilli, if you don’t want it spicy).
Add the vinegars and olive oil.
Cut the sundried-tomatoes into small slices and add these to the olives.
Season with salt and ground pepper.
Mix well, then transfer the olives and marinade into a sterilised jar, then seal.
Marinate in the fridge for at least 2 hours, preferably overnight. Keep chilled after opening.