BBC's six-year cover-up of secret 'green propaganda' training for top executives
> Pensioner forces BBC to lift veil on 2006 eco-seminar to top executives
> Papers reveal influence of top green campaigners including Greenpeace
> Then-head of news Helen Boaden said it impacted a 'broad range of output'
> Yet BBC has spent more than £20,000 in legal fees trying to keep it secret