Trewin was Founder and former CEO of the award-winning charity Hubbub UK which transforms the way environmental messages are communicated by bringing people and organisations together as a force for good. He is now CEO of Sizzle and a trustee of Carnegie UK. Previously Trewin created Global Action Plan the UK’s leading environmental behaviour change charity. Trewin was recognised as a Global Good Leader in 2020 and awarded a Lifetime Achievement Award in 2021.