A typical cup of black tea contains 40-50mg caffeine per cup, but this will obviously depend on the strength of the brew.
Green tea has less caffeine than black teas as it does not need as long to brew, however, it still contains caffeine.
The only decaffeinated teas that we offer are the Earl Grey and Royal Blend Teabags:
https://www.fortnumandmason.com/earl-grey-classic-25-decaffeinated-tea-bags
https://www.fortnumandmason.com/royal-blend-decaffeinated-25-tea-bag-box
However, all 12 of the infusions are decaffeinated (as they do not contain tea and therefore do not contain caffeine) and 4 out of the 6 of our botanical infusions are caffeine free (the two that are not decaffeinated are the Tempo and Grace).