The tea infusions (including the seasonal Plum, Apple and Cinnamon Infusion, 50g, the G&T tea and the Summer Cooler) do not contain caffeine as they do not contain tea, as the name refers to the process of steeping plants or fruits in hot water.
4 out of the 6 new botanical infusions are caffeine free (Nocturne, Repose, Rhapsody, Valiance).
https://www.fortnumandmason.com/tea/all-teas/caffeine-free?page=2