The Guardian has a good profile of the "Westminster Five" of Plane Stupid, who, in February, scaled the roof of the Houses of Parliament to demonstrate against the planned third runway.
Their quotes on the value of direct action are very interesting:
"In a situation where you need massive, urgent systemic change, we don't really have the system to achieve it," says Thompson. "Electorally, everyone is fighting over the middle ground. So the mere fact that you're not a moderate means you can't be listened to. That means anybody who had the answer to climate change would automatically be excluded from the debate. This is why you can't just think, if I vote for the greenest party at the election, I'll have done what I needed to."
Thompson adds: "If you look at the number of people who marched against Iraq, if you'd had 1% of that number taking direct action, they could have physically stopped the war. With 10,000 people sitting in the road at strategic points, you can bring the country to a halt."
"The reality of direct action is being prepared to put yourself on the line, and we need real casualties," Omond says. "If it's life imprisonment for going airside, if that's the penalty our society deems acceptable for someone protesting against a contributor to climate crisis ... then bring on life imprisonment."