Preheat the oven to 350 degrees F. Grease and flour a loaf pan.
Mix together flour, ground mustard, salt, baking soda, baking powder, and cayenne into a large bowl.
In a separate bowl whisk together egg, vegetable oil and beer and stir the batter until it is just combined.
Add the wet ingredients to the dry. Mix in the cheese and thyme. Pour the batter into the pan and bake for 45 minutes.
Let cool on a wire rack.