It's not that Lau and Lung are property-grabbing opportunists eager to cash in on their investments. They have lived and worked in Mirador for 40 years and consider the complex on Nathan Road part of their lives. Both are active in the maintenance of the building as members of the Mirador Mansions Owners' Corporation.

But the dilapidated state of their complex makes them worry about the future. Their frustrations are hardly alleviated by how neighbouring Chungking Mansions has stolen their thunder in recent weeks. Once considered the poor cousin of the two tenement blocks, Chungking - completed in 1962, four years later than Mirador - has just had the most sweeping makeover in its chequered history.

The estate, once notorious for its environmentally unsound guesthouses and illicit goings-on in shadowy passageways, now boasts a much-revamped appearance and an extensive security system featuring 208 closed-circuit television cameras and 30 guards.

By contrast, three plasma television sets (split into 23 smaller screens) stare down at the guards at Mirador's security office. 'This is all we have - 23 cameras,' says Nelson Mok Chi-wing, secretary of the owners' corporation and a resident for nearly three decades. They provide minimal protection for the occupants, monitoring only the exits and stairwells on the ground floor. The corridors of the building's deserted three-tiered shopping arcade are left unmonitored.

It's a shopping arcade in name only. The floors and their many corridors now comprise mostly small family businesses and travel agencies catering to people of South Asian descent. There's the odd fast food joint and several units manned by travelling African entrepreneurs packing goods destined for home. What permeates these floors, however, are things to which Chungking has waved goodbye: an unbearable heat radiating from the back of shops' air-conditioners and a nauseating stench from the unattended rubbish and makeshift 'toilets' - sometimes just the corner of a corridor.

The changes next door have left Mirador trailing well behind. As security guards impose a more stringent regime at Chungking, Mirador is inheriting some of the 'bad elements' who have simply moved up the street. Mok says there's been an increase in sex workers outside the building, and that dealers in drugs and counterfeit goods have relocated from Chungking.

It's all become too much for him, he says. Having withstood for decades what he describes as a 'pressure cooker' environment, he moved out last year, leasing his apartment. 'I'm leaving for the sake of my child - I want him to live in a place with better air and better recreational facilities,' he says. 'When I was growing up I never dared enter Chungking. Now, it's the opposite. When I was small, this place was populated only by workshops - you only saw the same set of people going in and out of the building. With the opening of guesthouses, it all changed.'

Mirador - whose Chinese name, Mei Lai Do, means 'the beautiful metropolis' - started out as one of the most prestigious addresses in urban Kowloon. Completed when Nathan Road was a leafy boulevard flanked by low-rises, the building consisted of flats of various sizes. The most expensive ones sold for about $59,000 when even the highest paid skilled workers earned about $300 a month.

The estate, zoned for residential and commercial use, was an address for the affluent middle class and light industrialists on the way up. A small community of tailors and textile traders still live and run small businesses in the building.

Mirador has provided the springboard for many a celebrity. Jackie Chan and Sammo Hung Kam-bo spent years perfecting their martial arts at the building's China Drama Academy, run by Peking opera stalwart Yu Jim-yuen. Ti Lung, who would find fame first as one of Shaw Studios' most bankable actors and later alongside Chow Yun-fat in John Woo's A Better Tomorrow, started out as a tailor's apprentice in the complex.

Mirador's fate has been tied with that of Tsim Sha Tsui, in general. And with the district sliding into the ravines of overdevelopment and the presence of the underworld, Mirador's prestige simply fell away. Type 'Mirador Mansions' into any internet search engine and one is bombarded with descriptions such as 'ramshackle warrens' of hostels, with rooms 'the size of a closet'.

Its decline is a textbook case of inner-city decay. As transportation links improved and Tsim Sha Tsui became crammed with gloomy high-rises, the building's upwardly mobile residents fled to the suburbs in Kowloon Tong or across Victoria Harbour. Taking their place were small guesthouses providing backpacker accommodation and businesses, some of a dubious nature. Today, the 16 floors house 752 units, consisting of about 300 on three shopping floors and the rest either guesthouses or flats, housing about 2,000 people.

'There's a joke here that you don't really have to leave Mirador Mansions to take care of all your needs,' says Mok. Not that it's an easy matter to get in and out of the building these days. Its small and slow lifts are barely big enough to accommodate the residents and visitors.

Mok admits that the owners' corporation is up against it in its attempts to reverse Mirador's decline, blaming selfish occupants who refuse to translate their concerns into financial support and government officials who fail to clamp down on the sex trade. 'I could easily have put in 208 cameras like Chungking did. They're just protecting their wallets when they turned down our proposal,' he says of some of the occupants.

A tour around the building reveals another major problem. The workshops of Lung and Lau, for example, are littered with plastic buckets and cardboard cartons to catch the water that seeps through the ceiling - a result of overloaded plumbing on the floors above. 'Every apartment that sits underneath a guesthouse is like this,' says Lau. 'They just divide a flat into six or seven en-suite rooms. Imagine what happens when all the guests flush or take a bath at the same time - the pipes just can't cope with the water. The sewage just seeps into the floors and walls - and the people living downstairs suffer.'

Mok also complains that the prostitutes operating in the building are mostly foreigners, pointing at the groups of south Asian and Mongolian women moving around the entrances.

Although reports suggest that foreign prostitutes have indeed set up base in Mirador - the most high-profile incident in recent years being a fight between two gangs of Mongolian pimps outside the building on Boxing Day 2002 - activists working with ethnic minorities in the area regard the concerns about foreign residents as 'contradictions in themselves'.

'Some [owners worried] that if they rented their places to south Asians fewer Hong Kong people would go there and start shops and businesses,' says Southern Democratic Alliance convenor James Lung Wai-man. 'But then again, if not for the south Asians who flocked to the building, the whole of Mirador Mansions would have just become another Jordan Plaza,' he says, referring to the deserted and ransacked shopping arcade on Jordan Road.

The building might be worn down, but improvements are afoot: the owners' corporation is considering tenders from contractors, with the hope of launching its own revamp in the next few months.

'Look at the chairman of the Chungking Mansions Owners' Corporation - she's just crazily dedicated to what she's doing,' says Sam Lau Kung-shing, chairman of the Tourist Guesthouse Federation of Hong Kong, a member of the Chungking group and also owner of several guesthouses in Mirador. 'If your work is transparent enough, owners will eventually support your every move.'