Ingredients:

2 1/4 ounces good quality gin (I like Tanquerey, 1 1/2 jiggers)
Tonic water, good quality
Lime wedge
Crushed ice
 
Method:

Fill double old-fashion glass with ice.
Wipe lime wedge around the rim of the glass.
Gently squeeze lime into glass and leave in glass.
Pour gin into the glass.
Fill with tonic water.
Here is the secret. DO NOT STIR! The essence of both gin and tonic mingle when you sip and it makes for a much fresher drink.