'We can't even give orders anymore the way we used to,' he said sadly, 'although we can still try to influence them.' The characters for 'bus' are now entering into Mandarin as a shameful import from Hong Kong where the Chinese language has long been corrupted by foreign devils. The long struggle by the party to maintain the purity of the language has become hopeless in the face of an invasion of CDs, books, and videos from Hong Kong and Taiwan.

Everyone here now talks of getting on a ba si and a minibus is a xiao ba or small bus.

The new buses competing with the public bus service are run by the privately managed Beijing Bus Stock Company and also by the Hong Kong City Bus Company. In fact, they represent the Trojan horse for an even more serious linguistic crime perpetrated by Hong Kong's Cantonese.

Taxis on the mainland have gradually stopped calling themselves qu zu qiche (vehicles for renting out) as they are supposed to and instead painted the characters di shi on the side. This is gibberish in Mandarin but in Cantonese the characters are pronounced to sound like dik si or taxi.

'In the 1970s and 1980s, many linguists said we should not use di shi but we now realise that these things follow their own logic,' the language commissar said.

Yet both ba si and di shi cannot be listed in any mainland dictionary and party-run newspapers are forbidden to use them.

For a while, the party even banned Hong Kong developers from naming their residential blocks the so-and-so garden (huayuan) because here in the north a garden means a park and certainly not a concrete tower block.

The authorities were stern in ruling that upstart Cantonese developers must also stop calling their buildings the so-and-so plaza and stick to the right word for square - which is guangchang, as in Tiananmen Guangchang.

All this seems to have been ignored by Hong Kong tycoon Li Ka-shing when he named the huge edifice erected next to Tiananmen Square the Oriental Plaza. A spokeswoman explained: 'We are really big and we have real squares not like those other developments which are just a single tower.' Besides, she said the language police never came knocking, a remarkable oversight for a party which used to pride itself on the fact that, like the ruthless Qin emperor, it had standardised the characters and unified the meaning of words.

Now the pendulum is even swinging the other way. Beijingers are trying to claim they were in fact the first to invent certain Hong Kong words, such as MTR. A spokesman for Beijing's grubby underground system was frank: 'I can't say Hong Kong copied it but we used it first. Foreigners just mistranslated our name as the Beijing Subway Company when it is really the Beijing Mass Transit Railway Co.' As Confucius wisely observed about the rectification of names: 'If the names are not correct, language is without an object. When language is without an object, no affair can be effected.'