Boil water, lemon thyme and blueberries for 10 minutes at medium heat without lid. Stir fruit and add sugar.
Boil until you get big bubbles, this means that the syrup has thickened. But be also aware, as this passes quickly and it may suddenly boil dry. So keep an eye on it.
Add the syrup to a glass and serve with Castello Tickler Matured Cheddar.