Marinade for chicken breasts

Just been watching a food programme and there was a nice sounding marinade for chicken breasts to use before grilling/bbq. If like us you have the winds then it is indoor grilling.

1 cup balsamic vinegar
1/2 cup tomato ketchup
1 tablespoon wocestershire sauce
1 tablespoon brown sugar
1 teaspoon mustard
garlic to taste one or two cloves.

Bring everything to a slow simmer and cook for 15 mins or until thickened then just pour over you chicken breasts.