Movie beauty Thandie Newton has joined the ecological crusade against 4x4 vehicles - and is writing to stars including Madonna and Tom Cruise to persuade them to join the campaign. Newton, 33, was converted after finding a Greenpeace sticker on the BMW X5 SUV she used to drive through London, detailing the damage such cars cause. She ditched the vehicle and now spends her time spreading the word. In a campaign letter she writes, "I loved my X5, loved driving it and what's more believed it was safer for my kids, until I discovered the truth about its impact on the environment. "Climate change, which is largely brought on by greenhouse gases in the atmosphere, seriously threatens generations to come."