"HIS wife in Hong Kong doesn't want to know, and the one in Shenzhen doesn't care as long as she has a little apartment," said Mr Tsang, a railway commuter at the border crossing, nodding to a businessman speaking on a mobile phone nearby.
He was explaining a phenomenon of the opening up of the border between Hong Kong and Shenzhen to commerce in recent years. Many businessmen and lorry drivers from the British territory have acquired cheap apartments on the Chinese side and installed young women from Shenzhen, giving the city the nickname "Second Wife Village".
Shenzhen police recently had to rescue a Hong Kong kidnap victim, a Mr Leung, who was snatched and held for $62,500 while on a rendezvous with his mistress.
Shenzhen is the restless boom town which has emerged from the paddy fields in Guangdong Province just across the border from Hong Kong. Set up as a special economic zone in 1979, it grew from a rural community of 70,000 people to a city of three million in just half a generation.
The gleaming, high rise city is an airlock between communist China and Hong Kong. A rusting barbed wire fence separates Shenzhen from Hong Kong - and this will stay after Hong Kong reverts to China in July - but it is also fenced off (electrically) from the rest of China to keep the population figure under some control.
At first glance it is almost indistinguishable from Hong Kong. Arriving from the Lo Wu rail terminus on the Hong Kong side, the first thing I saw when crossing a footbridge over the frontier was a billboard of Jack Nicklaus advertising the Mission Hills Golf Club.
Just beyond is the modern - Shangri-La Hotel, where a coffee (with orchestra) costs US$8 (£5). But prices are generally cheaper in Shenzhen than in Hong Kong. A room at the Shangri La costs the equivalent of £75. In Hong Kong it would be £200.
With 600 buildings above 18 storeys, the skyline is almost like Manhattan. There are shopping malls and stylish restaurants. In the suburbs there is a giant new Wal Mart, the first Chinese outlet of the world's biggest retailer where red vested "associates" greet customers with the required American "six tooth smile".
On the tree lined boulevards men and women executives drive around in Audis and Mercedes Benz. Many of the slightly battered taxis are right hand drive, having been imported secondhand from Hong Kong. Unlike Hong Kong, however, Shenzhen has bicycles, ramshackle trucks and old fashioned Chinese road discipline. I saw a pedi cab going the wrong way on the fast lane of a new highway outside town.
Completing the picture, most vendors deal in Hong Kong dollars, and on January 1st the Chinese system of charging foreigners higher prices for hotels, public parks and other amenities, which still applies elsewhere, was dropped.
Shenzhen has one of only two stock exchanges in China, the other being in Shanghai. Opened on July 3rd, 1991, the stock market fed the boom, turning private savings into capital investment. At first demand for shares outstripped supply.
There were riots in August 1992 when over a million people queued to buy lottery tickets for the chance to buy shares and corrupt officials snapped up tickets. The mayor and the party secretary were removed. Now there are trading counters all over the city, like bookies' shops, especially on Red Lychee Avenue, called locally "China's Wall Street".
It was in Shenzhen that Deng Xiaoping relaunched the Chinese reform programme in 1992. His face, too, beams down from billboards, competing with Jack Nicklaus. Deng is popular here. "He made people rich," said a retail buyer.
The author William Overholt tells in China, the Next Economic Superpower of an American lawyer being asked by a peasant for advice - he had sold his interest in paddy fields in return for an interest in a new factory and wanted to know where to invest his $200 million.
Life is so good here now that some Chinese people have returned from Hong Kong to live on the Chinese side. Many commute every day. Incomes in Shenzhen are much lower than in Hong Kong but still five times the national Chinese average. Unlike other Chinese cities, anyone who buys a flat in Shenzhen can live there, so some Hong Kong people have moved their Chinese relatives from other parts of China to be nearer.
Shenzhen's transformation has been made possible by Hong Kong finance, management, marketing, design and technology. Some 80 per cent of investment in Guangdong comes from Hong Kong. Thousands of foreign companies have set up joint ventures in the zone, where wages and services are cheaper and there is ready access to the huge Chinese market.
Typical of these is Thermo King, which makes transport refrigeration units and of which Jinshan Chen is the Shenzhen plant manager. It was set up in 1993 by the Irish staff of the Galway plant of the Minneapolis based company. Having worked both in China and the US, Mr Jinshan knows both systems, essential to running any joint venture in Shenzhen.
"Life is very close to the western level here and you can maintain whatever living standard you want," he told me in his office in Chegongmiao industrial zone. But the restlessness of the workers, many of whom the company sends to Ireland for training, is a problem.
"The turnover rate of people is very high. They are always moving on looking for a better salary, better housing. Everyone considers their work a temporary job," sighed Mr Jinshan.
"The people in Shenzhen are so dynamic, always trying to find a better life." He smiled in a resigned way and added, "That is China in transition."