Prepare peaches and set aside. I like to wash the peaches well to remove the tickly fur, but leave the skins on.
Place the EVOO and onion into a shallow frying pan on a medium heat and cook the onions until just caramelising.
Add the spices, brown sugar and cook until fragrant, stirring.
Add the vinegar and peaches and cook for a few minutes covered until the peaches are cooked but still holding their shape. Stir in the thyme leaves and allow to cool slightly before dividing between sterilised jars of choice.
These make a lovely present, and the relish is fantastic on the Christmas table with seafood or turkey, ham etc.