Complex sentence: John Stewart a veteran of Twyford Down, is chairman of the Campaign for Better Transport (UK) and AirportWatch and is involved in other aviation related protest groups, such as HACAN Clearskies and Stop Heathrow Expansion.
Split into simpler sentences: John Stewart a veteran of Twyford Down, became chairman of the Campaign for Better Transport (UK) and also of AirportWatch. He is also involved in other aviation related protest groups including HACAN Clearskies and Stop Heathrow Expansion.