In the simmering heat of a Manila July, a wealthy Chinese fugitive was, until late last week, confined to a grim isolation cell in one of Asia's most notorious detention centres, giving him plenty of time to contemplate a potentially deadly dilemma: should he stay or should he go home?

Wang Bo's downfall was sudden and brutal. Six months ago, the crop-haired 31-year-old was jetting between China and the Philippines, allegedly running a multimillion-dollar transnational illegal gambling business that the Chinese authorities accuse Wang of having used China-issued bank cards to fund.

On February 5, he was intercepted by immigration officials as he arrived in Manila because the Chinese passport he was holding had been cancelled. He was taken to the Bureau of Immigration's detention centre in Bicutan, Taguig City, in the south of Manila, to be processed for deportation.

Since then, he has spent most of his time locked up in a grey, airless isolation cell in a facility that once served as an extermination centre for opponents of the Ferdinand Marcos regime.

Other inmates are packed into tiny rooms; there is no privacy, nowhere to exercise and nowhere to escape the oppressive humidity and the stench of fetid close-quarter living.

Never formally charged with a crime, some of the 150 or so foreigners held here disappear into an opaque legal whirlpool and remain locked up for years or even decades. These inmates are known as The Forgotten.

It couldn't be further from the playboy lifestyle Wang reportedly enjoyed before he was stopped at Ninoy Aquino International Airport. And yet it seems he was prepared to do anything that his money and influence would allow to stay among The Forgotten. In China, he faces the death penalty for illegal gambling and embezzling US$100 million.

Wang has been accused by The Standard, a Manila newspaper, of handing 100 million pesos (HK$17 million) to Bureau of Immigration officials and US$10 million to lawmakers in bribes to try to avoid deportation, in a case that has led to a series of inquiries and disciplinary action against three officials.

As he sweated it out in solitary, before the Philippines bowed to Chinese demands for his deportation, Wang's case helped shed light on the peculiar detention centre in which he was being held.

Nikolaos Spanoudis, who ran a call centre in the Philippines employing 400 people, spent 18 months in Bicutan, where he was held as an undesirable alien. Now back in his home country, Greece, he is pursuing lawsuits against the Bureau of Immigration for illegal detention and has lodged a case with the United Nations Human Rights Council over his treatment.

Picked up because of United States drugs charges dating back 20 years, he claims officials demanded US$50,000 then US$100,000 for his release and told him if he did not pay up he would "rot" in Bicutan.

"You see people there who have been inside for seven, 11, or 14 years," he says. "When you talk to them, you discover they have never faced a criminal charge.

"The officials basically use these people as a warning to you. They tell you: 'You see? This is what happens when you don't pay. You will be here for the rest of your life and you will be forgotten.' It is psychological and mental torture."

Describing conditions inside Bicutan, Spanoudis - who was detained from 2012 and was later cleared of involvement in an alleged cocaine smuggling plot in the US - says, "It was where Marcos' opponents were killed. From what the guards tell us, there is an area the bodies were thrown into, like a septic sewer thing. There are hollow areas beneath the floor in some places and you can tell something is below."

The centre is situated in the middle of the Manila police headquarters, with 2,000 officers housed in blocks surrounding it and a firing range outside the entrance.

"The firing goes on day and night - you hear bullets and guns going off constantly," says Spanoudis, 51, who now runs a website and a Facebook page called Foreigners for Justice, aimed at exposing corruption in the Philippine judicial system. "Bullets sometimes ricochet off and land inside the centre. You get no peace and it's very unsettling.

"It is a very stressful and unhealthy environment. Three people had strokes when I was there. Drug use is widespread. The guards help bring it in for the drug dealers. Every once in a while there is a raid. Then, later, they sell it back to the dealers inside the centre."

Spanoudis was sent back to Greece and held for 10 months pending deportation to the US.

"When I got to Greece, I was put into one of the worst prisons imaginable. I was in there with Albanian and Russian gang members and terrorism suspects," he says. "But you were fed plenty of food and they gave you proper medical care and there was a soccer stadium area to run and exercise in.

"In Bicutan, you were given a handful of food every day and there was only one telephone for 170 inmates and office staff to share. Conditions in Bicutan are just atrocious. When US embassy [officials] came to see me in Greece and asked how I was being treated, I said, 'This is the Hilton compared to the Philippines.'"

It's visitng time in Bicutan on a Saturday morning. The fierce summer sun beats mercilessly down on the plastic sheets draped over an open courtyard as shoeless inmates in grubby shorts amble wearily out of their cramped cell blocks to sit on plastic chairs with visitors in a caged enclosure.

In the courtyard beyond the wire, groups of Asian inmates play cards or shoot pool on a ramshackle table while Westerners chatter furtively in small huddles, exchanging cigarettes, books and contraband. The centre is home to a colourful mix of detainees from countries that, last month, included Australia, Britain, Bulgaria, Canada, the Czech Republic, Germany, India, Italy, Japan, Korea, Liberia, Nigeria, Pakistan, Palestine, Papua New Guinea, Romania, Russia, Sudan and the US. Prisoners from Hong Kong, Taiwan and China are here, too.

I have come to speak with Briton Gypsy Nirvana, who has been held for more than two years awaiting extradition on charges of selling marijuana seeds by post to buyers in the US, and American Arthur Benjamin, the former owner of a bar in Subic Bay who has been held for 2½ years since being arrested for allegedly hiring underage girls and having a 16-year-old girlfriend. They point out some of the other characters who have had to call Bicutan home.

Paulo, an Italian in his late 60s, used to work in the Italian embassy. He was detained as an overstayer after a dispute with his Filipino ex-wife. Looking like a bemused John Hurt, he has now been held for years for reasons no one can fully understand, and shuffles aimlessly around the courtyard in a ragged striped shirt and a broken pair of eyeglasses.

Another inmate is the bearded Guru Jara Dobes, who drifts around the courtyard and speaks earnestly through bars to a woman disciple held in the separate female section of the centre. Arrested in May, Dobes, 43, has been on the run since 2007 and has resisted attempts by immigration officials to deport him to his home nation, the Czech Republic, where he allegedly raped scores of women and had sex with 350 who joined his sect and were told they would be spiritually cleansed by the experience.

After he transferred his sect to Asia, a female assistant is said to have helped him recruit more women here to have sex with.

"He just seems to be a very peaceful guy who does a lot of meditating," says a fellow inmate.

Out of sight of the visitors' area is a mysterious Russian inmate in his 70s who has not left the second floor of the centre, where his shared room is located, for two years and claims to hold a Knights of Malta passport. Also in residence is a widely reviled and feared Hong Kong drug smuggler rumoured to be the centre's leading shabu (methamphetamine) dealer.

One foreigner especially determined to avoid deportation is 73-year-old Briton Douglas Slade - the notorious co-founder of the 1970s movement Paedophile Information Exchange - who faces a long list of child sex abuse charges back home. Slade fled to the Philippines in the 80s and has been arrested for abusing underage boys on a number of occasions but has always evaded justice, on one occasion boasting to a television reporter of how he had bribed officials to be released from prison.

Wealthy and weighing 158kg, Slade runs a successful meat-distribution business based in Angeles City and has pork pies delivered to him by his employees. He has told fellow inmates that he will escape deportation and has tried on a number of occasions to secure a transfer to hospital for treatment for diabetes-related health issues.

Nirvana, 54 - who, in the 80s, lived in Hong Kong, where he acted in kung fu films - is fighting deportation as he fears he may not see his Filipino wife and children again if he leaves the country. He says he has been told he can be deported to Britain if he drops official complaints he has made over his detention and the handling of his case, a move that could see him permanently excluded from the Philippines.

"The heat here is very oppressive," he says. "There is no air-conditioning, and in the heat of the day temperatures can reach or exceed 40 degrees Celsius on the top bunk-house floor, under a tin roof that leaks when it rains.

"Every inmate is allowed one fan, but when it gets so hot, that fan just blows hot air. Often there are brown-outs [power cuts]. Most mornings you wake up in a sweaty bed because it's too warm, even at night, for most Westerners. Taking a nap during the day guarantees a sweat-soaked bed for most of the year.

"Every day is pretty similar," he says. "You can lie on your bunk, or the floor for 24 hours per day if you like … There isn't much intrusion or interaction from the guards or anyone outside, unless you're lucky enough to have friends or family that want to visit you, or a lawyer, if you can afford one.

"Many here are what we call 'The Forgotten' - inmates completely stuck within the system and who seem to be useful only to the Bureau of Immigration, so that they can keep their quota up and receive a generous budget from the government.

"Even if an inmate does have a lawyer, and that lawyer is one of the very few who is proactive about advancing a case, they have to deal with a corrupt, constipated and mostly inept legal system that is almost impossible to navigate within any sort of reasonable time frame.

"A few of the inmates just pace around all day like caged animals in this human menagerie - like the walking dead - not knowing when or if they will ever get out of here."

Benjamin was arrested in a sting orchestrated by US and Philippine police, and in which TV reporters posed as customers; it was broadcast on American channel ABC News. However, the case against him has stalled, he says.

"I am going to be here until my case is dealt with. The last guy with a case like mine was here for 8½ years. I feel life is passing me by. I've been here nearly three years. I turned 50 inside - my wife turned 50. My kid went to college. I will win my case here because they don't have any real evidence against me but, when I win, they will deport me and I'll be tried again in the States for the same charges I have been found innocent of here.

"My wife has stood by me despite what has been on TV on four continents and brings me stuff and makes sure I am comfortable. We had some issues, of course, but I talked to her about it and she said, 'I am your wife and I will stand by you.'

"My brothers and sisters say they don't want anything to do with me," he says. "People I considered friends don't return my emails. People I thought I knew really well refuse to talk to me at all. My Christmas card list is extremely short now but that's OK. It's good to know who your real friends are."

For The Forgotten, and others here struggling to make sure their cases are remembered, an uncomfortably long, hot summer in Bicutan drags on and on.

Red Door News Hong Kong