Firstly make the raspberry syrup. Place the raspberries, 1 cup of water and 1 cup of sugar into a deep saucepan over a medium-high heat. Bring to a boil and then turn down the heat slightly. Continue to simmer until the rasberries break down and become mushy. A few larger lumps are fine as you'll sieve it.
While the rasberry syrup is heating up, boil the kettle with 3 cups of water. Place 6 tea bags and 1/4-1/2 cup lemon juice into a large jug. I would add 1/4 cup first and then add more if required. Pour the 3 cups of water onto the tea bags and leave to brew for 3-8 minutes, depending on how strong you like it. Once brewed, add in the bicarbonate of soda. This will take away some of the bitterness of the tea.
Leave the lemon mixture to the side. Place a sieve over a large jug and pour the raspberry mixture into the sieve. Strain until all you're left with is raspberry pulp and seeds in the sieve.
Pour the raspberry syrup into the prepared lemon tea mixture and then add 2 cups of cold water. Leave the Raspberry Lemon Iced Tea to cool for at least 30 mins, then transfer to the fridge to chill for at least 90 minutes.
Once chilled, place a few ice cubes into a glass, pour the Raspberry Lemon Iced Tea into the glass, drop in a couple of raspberries and placee a slice of lemon on the rim of the glass.
Iced Tea will keep in a covered carafe/jug in the fridge for 3 days. Best servd chilled.