When we heard that Thom Yorke was going to be aboard the Rainbow Warrior from Amsterdam to London, you could spot the Radiohead fans: they were the ones who fell over onto the helideck like planks. OK, I exaggerate. One hit that stuttering staccato "Creep" power chord on air guitar. Another was literally jumping up and down. Another tweeted "Thom Yorke aboard. Must not embarrass self." Harmony, one of our New Hands on Deck, eloquently texted a world record number of repetitions of "OMG OMG OMG OMG."

Of course, once in his presence, we were all, you know, cool. He was aboard as our guest, our way to say thank you for support he's given Greenpeace and for his contributions to efforts against climate change and his work on fair trade issues -- we tried to give him a great experience of our new ship, and were careful not to mob him with requests for photographs and autographs, or pester him with all those questions we were dying to ask.

As it turned out, he was a humble, very cool person to have on board, and as clued up about environmental issues as any of us. He spotted 350.org's website over my shoulder. He wanted to be kept updated on the Keystone pipeline. He told us about his foray into the Copenhagen climate talks with Friends of the Earth, disguised as a journalist.

New hand on deck Harmony was worried she was being too cool, and that one of her musical heroes might think she didn't know who he was. But even the crew who really didn't know Radiohead or recognise Yorke were struck by what a nice bloke he was.

Me, I was struck by that as well, and by something he said to the Telegraph: "This is no hippy tugboat. This is some serious shit." And as others have observed, he's right. This ship is run tight, it's a triumph of technology, everything from sail trim to emergency reefing drills is about precision, measurement, improvement.

But the hippies are also here in spirit, and I'm proud to count myself among them. 40 years ago, hippies founded Greenpeace. I was ten years late to that party, but it was still roaring with hippy energy.

If that sounds like a dig, you're tuned to the wrong frequency, Kenneth. Don't believe the cartoon image that has come to dominate the popular image of hippies: the unwashed, lazy, spliff-befuddled park litter looking for a handout.

Sure, that was there.

But the hippies that founded Greenpeace were of a different sort, of a tribe that was a major cultural force which history has largely forgotten: nonconformist visionaries who simply refused to accept that things were as they were simply because that's how it was, nor that they had to do as they were told simply because someone claiming authority had told them to do it.

They were men and women, not all wise or good, who valued peace over nationalist zealotry, love over money, nature over things, and were willing to risk their security, their social standing, and in some cases, their lives, for what they believed. And they had the creativity and the energy and the persistence to pursue those visions to the end of some very elusive rainbows.

Over the years, Greenpeace has struggled with an identity crisis that founding member Bob Hunter identified as "the mystics versus the mechanics" -- between the values of hard-headed political realism, efficiency, and critical pathways, and those who see themselves as part of an old Cree prophecy about a tribe of warriors who will heal the earth when it is sick.

The Rainbow Warrior is both a triumph of the mechanics, and a testament to the mystics.

When another one of our new hands on deck, Pablo, heard Thom Yorke would be aboard, he remembered seeing an interview in which Yorke was bicycling around New York City ("not the most bike-friendly town in the world" Pablo observed) and had said "You can be an activist all by yourself, simply by the choices you make in your daily life." That was something that stuck with Pablo, and was partly inspirational to him in eventually choosing to work for Greenpeace and dedicating himself full-time to environmental activism.

On arrival in London, I finally got the chance to ask the guy who wrote "the planet is a gunship, in a sea of fears" a few questions on camera. I told him that Pablo had been inspired by him, and was aboard the Rainbow Warrior partly because of the example he had set.

zoom Thom Yorke and Pablo Bullrich

"I'm glad to hear that I might have inspired someone to be an activist all the time," he said, "because I'm not, I can't be. But the world needs more people like Pablo."

True. And the world needs more people like Thom Yorke as well, and people of his ilk. You can call them what you like: I call them hippies.