Jezza Neumann on undercover reporting: 'It's hard to explain that fear in your gut'

It's illegal to work as a journalist in Tibet, so we knew that it was going to be a struggle even to get there, let alone to survive and report.

If you want to film in Tibet then you have to apply for permission, and if you're given permission then you'll be allocated a state-appointed minder – so the only way to make a film of the truth successfully is to go undercover.

As China shows its friendly face to the rest of the world in the year of the Olympics, our mission was to show people what was really happening. Were the Chinese authorities being honest about the way they govern Tibet? Or should we believe the reports from the human rights activists, campaigning to free Tibet from Chinese rule and oppression?

I have worked undercover in China, to make last year's Dispatches documentary special China's Lost Children. This was 10 times more difficult.

To get to Tibet, you either have to go through Nepal or China, but as there's only one road from Nepal, which is heavily policed, we chose to go through China. And in order to get in to the Tibetan Autonomous Region (TAR) – the area that the Tibetans are fighting for – you need to apply for a pass. But if you fill in the form and say that you're a journalist, you've no chance of being issued one, so we had to convince the authorities that we were tourists.

The key to the door was Tash, a 30-year-old Tibetan refugee who lives in London and whom I'd met two years ago after he escaped from Tibet by walking for 24 days across the Himalayas. Tash had seen refugees shot dead for trying to leave Tibet in 2006, but he wanted to go back to see if things had changed.

We landed with a bang. Our first contact rang us to say that the location we had planned to meet at wasn't safe, so he would rearrange it somewhere else.

I wasn't prepared for that: before I'd left Britain, I'd put together a 15-page security document, which I'd imagined covered every conceivable scenario and risk.

Now I had to cling to one thought: if you can't trust people who have put their lives at risk to talk to you, who can you trust? Without that belief, we might as well have just gone straight back home.

From reporting China's hidden trade in children, I'd learned important lessons in avoiding the attention of the police. So we were strict in deploying our anti-surveillance techniques. We used different phone numbers and email addresses for each contact, and met them away from where they lived to reduce the opportunities for the spies that might be tracking them. I learned last year that there are spies everywhere in China, but in Tibet it's a whole new story.

We spoke to a cross-section of the community: a student, an ex-political prisoner, a nomad and a monk. Each of them spoke of the fear in which they live. One Tibetan had been arrested and jailed for seven years for giving out pro-Tibetan leaflets. In prison, he was stripped naked, handcuffed and put in a pool of water that his captors then electrocuted. That was just for putting together a leaflet. As he was recounting the story to us, he just broke down.

We also spoke to a monk, who told me that he was constantly being watched and monitored in his monastery. The secret police would go to his room without warning, and search it for anything that mentioned the Dalai Lama. He said that a fellow monk who was found to have written "Free Tibet" on a book subsequently went missing for three years. The riots taking place now in Tibet have been boiling for a long time. These monks aren't thugs on the streets, but seriously oppressed people who saw an opportunity to release the pressure they were living under.

China maintains that it doesn't implement its one-child policy in minority regions such as Tibet, but we discovered that this wasn't true. One woman told us how she'd been subjected to a forced sterilisation. The secret police broke into her house and said they would take all of her belongings if she didn't go with them. Aspirin was the only anaesthetic she was given before they cut her open. We'd also seen reports of mobile sterilisation units in Tibet, though we didn't find anything further to substantiate that.

There's such a massive adrenaline rush whenever you do one of these operations, but it was only when we thought we'd been caught that we experienced something akin to the fear in which these people have been living for years.

During an interview we were conducting, there was a knock on the door. When the interviewee thought he recognised a man outside as a member of the secret police, we all ran off in different directions. I ate the piece of paper with the contact phone numbers on, a piece of paper that we had previously kept in Tash's sock.

Having made our escape, we felt we had to protect our work by going to the top of a mountain with the tapes we'd recorded and burying them beneath a pile of rocks. We came back for them a day later, not sure whether they'd been taken, whether police might be waiting for us. It's hard to explain that fear, a gut feeling that goes through your whole body. It's like that constantly in Tibet, wherever you go.

The act of hiding the tapes convinced me that it was time to call it a day and head home to Britain. We hid the footage on the hard drive of a computer for the journey home, knowing that we had filmed something that would help to reveal the real truth of Tibet.

'Dispatches: Undercover in Tibet' is on Channel 4 tonight at 8pm. 'China's Lost Children' is nominated for five Bafta television awards. Jezza Neumann was speaking to Amy Fenton