Press the mint into the palms of your hands to release the aroma and place it in the bottom of a tall chilled glass.
Slice the lime and place on top of the mint, then add your bought or pre-made simple syrup and give it a good mix, crushing the lime juice and mint gently. .
Fill glass ¾ with crushed ice to bring out the flavour, then add your Welsh rum and top up with soda. Garnish with a sprig of lemon and a wedge of lime and enjoy.