Beijing goes into lockdown as Communist Party prepares for once-a-decade transition of power

As China announced the date for its once-in-a-decade change of leadership on Friday, Beijing was already moving into lockdown.

The city's estimated 10,000 to 20,000 armed paramilitary police have been put on the highest level of peacetime alert, with all holiday leave cancelled, and all arms and ammunition to be kept ready.

Meanwhile, security has also reportedly been raised for the elite group of men who are expected to form China's next Politburo Standing Committee, the all-powerful collective that leads the country.

Extra security has also begun for flights and trains both in and out of China's capital.

Not only are bags being checked randomly outside airport terminal buildings, but all passengers are subject to an extra layer of screening inside. At train stations, all bags are being opened and inspected.

The provinces around Beijing have mobilised units to man the highways into the capital. Freight vehicles have been banned from carrying toxic chemicals into Beijing until the Congress is over. Other provinces have also issued special notices to "prevent major incidents threatening national security and social stability".

Hu Jia, one of China's most high-profile dissidents, said he had been beaten three times by police, put under house arrest and had his internet cut. Hebei, Beijing's neighbouring province, said it would do its best to keep "suspicious people and problematic people" inside its borders. The scrutiny extended to the Bookworm, a foreign language bookshop and lending library, which has had to remove all books about China from its shelves.

However, Beijing will almost certainly be a prettier city for the next five weeks. More than 20 million pots of flowers are being deployed in intricate decorative walls that spell out the arrival of the Party Congress. Banners have been slung to exhort residents to respect the Party, while volunteers will fan out across city to keep order on the roads, blowing their whistles at jaywalkers.

The leadership transition may also be good news for Chinese investors. The Shanghai Stock Exchange is expected to tick up as the government bolsters confidence ahead of the Congress.

What is a Communist Party Congress?
More than 2,200 delegates descend on Beijing to discuss the party's policies. Promotions and demotions have featured, and in 2002 the event was used as a platform to unveil a new leadership. This year, a similar transition is due to take place. In China, the Congress is known as the "big meeting", or just by the Chinese character "Da", which means "Big". This year is the "18th Da".

How often do they take place?
Since Chairman Mao's death in 1977, the meetings take place every five years. The practice is to tee up future leaders in odd-numbered congresses and announce them in even-numbered ones.

What happens?
It is a bit of a mystery. Apart from the opening and closing addresses, everything takes place behind closed doors. In addition, most if not all of the big decisions have been ironed out well in advance. Two things can be counted on. There will be very long speeches, and, at the end, the Politburo Standing Committee will walk onto the dais in order of seniority. This year, the seven leaders are expected to be Xi Jinping, Li Keqiang, Yu Zhengsheng, Zhang Gaoli, Zhang Dejiang, Li Yuanchao and Wang Qishan.

How does the Congress work?
Local congresses have been held in each of China's provinces and autonomous regions (such as Tibet and Xinjiang) and have selected representatives to send to Beijing. No more than 68 per cent of the delegates may hold leadership positions in the party. The other 32 per cent should be "grassroots" party members who hold jobs outside of the party apparatus. The Congress will choose who sits on the 200-person Central Committee, and who its 180 or so alternate members will be. It also chooses the 25-man Politburo and the Politburo Standing Committee, which could shrink to seven men again this year.

Which generation of leaders have we reached?
Taking Chairman Mao as the first generation, the new leaders will be the fifth generation, the first to be born during the Communist era. Unlike the fourth generation of engineers and economists, many of the new generation are social scientists. A large number are also "princelings," the children of former Communist leaders.

Who's in, who's out?
This year will see a dramatic upheaval. Out of the 25 man Politburo, 14 are due to retire. In the Politburo Standing Committee, seven out of nine will step down. At the same time, 70 per cent of the leaders of the Central Military Commission, the party arm that runs the People's Liberation Army, are due to stand down.

What happens to Hu Jintao and Wen Jiabao?
Hu Jintao has moved to consolidate his network of power in the run-up to his retirement, filling the heights of Chinese politics with his proteges. Both Deng Xiaoping and Jiang Zemin wielded enormous power and influence after they retired, and Mr Hu may be hoping to follow their example. Mr Wen's position is less clear. He has used his final year in office to press for reform instead of hustling for position.

Additional reporting by Valentina Luo