The journalists' rule of thumb in China is that you cannot report the so-called three Ts - Tiananmen, Taiwan or Tibet. But it turns out there is also another T that upsets Chinese censors.
Jeff Sun is the scion of one of China's new rich and the founder of the "China Super Car Club". He has got so many he cannot even remember them all.
With a bit of head scratching he can list the two Lamborghinis, the two Ferraris, the Audi R8 and the Maserati. But then there is a long pause before his face suddenly lights up.
"Ah yes," he says, "and the Bentley".
We met Jeff while reporting on the yawning chasms of inequality that have opened up in Chinese society.
We filmed in some of the poorest communities I have ever visited - Chinese villages where no-one has ever owned a car and where they still till their fields using a single donkey, shared between dozens of farmers.
China still claims to be a communist society and has a fearsome reputation for censorship, so why was it happy for us to do this?
The answer says a lot about both China's ambitions and the challenges the country faces.
A couple of years ago I made another series, this one about China's great expansion into the world over the last decade.
I had not expected the Beijing government to like the films. We met some very sympathetic Chinese people but we showed the corruption and brutality of others.
Yet, shortly after the programmes were broadcast, I received an email from a senior official at the Chinese embassy inviting me to tea at a London hotel. It said the Embassy had liked my programmes.
In the genteel grandeur of the hotel the embassy official told me why.