Ingredients:
45 ml scotch
25 ml sweet vermouth
1 Maraschino cherry
1 dash Angostura bitters

Preparation and serving:
Combine all ingredients in a shaker with ice cubes. Stir and pour in to a cocktail glass. Garnish with Maraschino cherry.

Variants:
Dry Rob Roy: dry instead of sweet vermouth
Perfect Rob Roy: equal parts dry and sweet vermouth