Fill a highball glass with ice.
Add gin, fresh lemon juice, and simple syrup directly into the glass.
Stir gently to combine.
Top with soda water and give one final gentle stir.
Garnish with a lemon slice and a maraschino cherry.
The John Collins predates the more famous Tom Collins - originally made with Old Tom gin rather than London Dry, lending it a slightly sweeter, more rounded character. Using Old Tom gin is a great way to honour the original recipe.
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