Pour 150ml cold water into a large heatproof jug then top up with 450ml boiling water. Add the tea leaves and leave to steep for 2 mins.

Meanwhile, fill your teapot with boiling water to warm it. Once the tea has steeped, pour away the water in the teapot then add the grapefruit and rosemary. Strain the green tea into the teapot, leaving the tea leaves behind. Don’t throw the leaves away – you can re-brew them again for another pot that same day. (For the second brew, make sure you let the mixture steep for 3-4 mins.)

Let the grapefruit and rosemary infuse for a few moments, then serve. Add honey or agave syrup to sweeten if you like.