Put the raspberries, sugar and water into a large sauce pan.
Cook over medium heat, stirring every so often, for 20 minutes - until all of the sugar is dissolved.
If fruit is still chunky, mash with a potato masher or fork.
Pour the mixture through a sieve. Use the back of a spoon to smash the juice through, leaving the seeds.
Squeeze the lemons and strain the juice. Add to the raspberry juice.
Let the cordial cool in the fridge for several hours until cold.