The moment "Ken" walked into his first Plane Stupid meeting, we were suspicious. "He looks like a cop," said Kat. This was just after last summer's Heathrow climate camp and months before our banner drop from the roof of parliament made us everyone's favourite middle-class eco-revolutionaries.
Our mole's real name was Toby Kendall and we were happy to have him. Better the mole you know, as they say. However, he was awfully dedicated. He arrived at every meeting 10 minutes early (enough in itself to mark him as an impostor) and was very enthusiastic about everyone else being a bit more radical and taking more risks. Eventually Tamsin and Kat, stalwarts of our London group, decided they had had enough of acting as zookeepers and insisted we throw him out.
This is where it all became terribly embarrassing. We knew he was a mole partly because he dressed like a public schoolboy (with a keffiyeh added for activist cred), partly because there had been leaks from the group (planted by us to test our suspicions) and partly because "Ken" didn't seem to exist on the electoral register or anywhere on the internet. But we didn't have any hard evidence. "What if we confront him and he denies it?" was our common fear. Not that we thought we might be wrong, but it would be unbearably awkward.
Kat and Tamsin agreed to meet Kendall in a local Japanese restaurant. It was excruciating. I know, because I was hiding behind a bamboo screen, with my copy of the Guardian as an extra layer of protection. He just would not stop lying. He said how upset he was, that he felt he was being judged on his background (gulp), that he felt betrayed, that he had lost his wallet and his passport was at his mum's and he would prove his identity with a letter from his tutor at Oxford (apparently 007 always carries a note from teacher for just such an occasion).
We were on the brink of welcoming him back just to put an end to the whole ghastly, drawn-out charade.
However, we gritted our teeth, turfed him out, and then sent his photograph to a friend at his college in Oxford. Once we had his real name, the rest was easy. As it turns out, he was employed by some sort of elite industrial espionage set-up allegedly staffed by special forces veterans and called C2i International. (C2i has since denied that he infiltrated our group on its behalf.) We discovered all this via his social networking site, along with his favourite film: Top Gun.
· Graham Thompson is an activist with the campaigning group Plane Stupid.