Pre-chill a Collins glass.
Add 60ml London dry gin, 25ml fresh lemon juice, and 15ml rich sugar syrup to a cocktail shaker.
Fill the shaker with ice and shake hard for 10–12 seconds.
Fill the chilled Collins glass with fresh ice.
Strain the shaken mixture into the glass, simultaneously topping with 50ml chilled soda water to integrate.
Garnish with a skewered orange slice and maraschino cherry (sail) perched on the rim.
The John Collins predates the more famous Tom Collins - it was originally made with Old Tom gin by headwaiter John Collins of Limmer's Hotel in London around the 1860s; switching to London dry produces the crisper, drier modern version most bartenders serve today.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including John Collins.