Lightly toast cinnamon sticks in a skillet over medium heat. Set aside the roasted sticks after breaking them up. Pour a quart of Tanqueray into a clean jar and add the broken sticks. Allow this to settle for a few days before tasting and assessing. Remove the cinnamon stick once it has reached the appropriate level of spicy flavour.
Fill a cocktail shaker halfway with ice. Pour 15 mL cinnamon-infused Tanqueray London Dry Gin, 22 mL fresh lemon juice, and 1 tbsp orange marmalade into a mixing glass.
Shake the ingredients together until fully blended.
Fill a glass halfway with new ice. Fill the glass halfway with the cocktail mixture.
Garnish with an orange wheel and a cinnamon stick.