Boris Becker joined the diplomatic corps of the Central African Republic at a good time. In the midst of the turmoil surrounding the bankruptcy proceedings the indebted tennis star was grappling with in London, he was surprisingly named the attaché for sports, culture and humanitarian affairs for the country. "Diplomatic honors for me!" Becker announced on Twitter on April 27, 2018.

Among those congratulating the newly anointed diplomat included a certain Stephan Welk. He had worked his contacts for Becker and helped him receive the post. "Welcome to your diplomatic office," Welk tweeted, accompanied by a photo of him and Becker together in front of the Central African Embassy in Brussels, smiling under the republic's coat of arms, which features an elephant, a baobab tree and stars.

Welk is no stranger to lightning-fast diplomatic careers. Online, the 51-year-old from the German state of Hesse presents himself as a "professor for international law and diplomacy" who assists African governments as a "special adviser." He claims he has received multiple awards for his service, including the "Grand Cross of the Royal Order of the Lion of Rwanda."

At the moment, though, Welk's diplomatic services are unavailable. On August 30, he was taken into custody in Berlin, and two suspected accomplices were detained as well.

The arrests are the product of a case being pursued by public prosecutors in Munich, who have been investigating six suspects over the course of several months. The officials are part of the anti-corruption division, and they are tying to shine light on a shadowy world.

Several dubious businesspeople have succeeded in obtaining diplomatic passports and diplomatic service cards from impoverished countries. The recipients of the documents include well-known criminals who may have hoped that diplomatic immunity would protect them from the police or public prosecutors. It is thought that up to six-figure sums may have been paid for the documents.

Documents seen by DER SPIEGEL show that several Germans with dubious resumes have been appointed as supposed advisers and diplomats by African countries. At the center of the scandal is the small African country of Guinea-Bissau.

The country's government apparatus granted diplomatic papers to a convicted fraud and con man, a person who has declared bankruptcy and a boxer who has spent time in jail. The diplomatic documents carry illustrious titles like "economic adviser," "attaché for culture and sport," "head of security" and "diplomatic courier." Even Stephan Welk, who has a record of multiple convictions, was given a green diplomatic ID by the embassy in Germany, serial number GNB67D915.

The continual distribution of diplomatic documents from foreign countries has long been a source of concern for the German government and the country's security agencies. The papers could enable criminals to try to cross national borders unnoticed and to avoid police checks or even arrest. Although immunity only applies once the diplomat is accredited by Germany, in practice the mere showing of a diplomatic passport can make an impression on some police officers. Cars with diplomatic license plates are also stopped less frequently by police than other vehicles.

Longstanding Problems

Inside the German Foreign Ministry, Guinea-Bissau has long been seen as a diplomatic problem child. Indeed, the country's embassy in Berlin had hardly opened its doors in 2012 before the police began making regular calls to the protocol division of the Foreign Ministry.

The division in the basement of the ministry is where the complaints end up. It's where German agencies and institutions turn to when diplomats violate the rules of their host country.

In the case of Guinea-Bissau, Foreign Ministry officials quickly grew suspicious. The police regularly reported traffic violations and other offenses that had been committed by diplomats from the African country. Frequently, though, those offenses were committed by German citizens, who were quick to produce a diplomatic document and to insist on diplomatic immunity. None of them had been accredited by the Foreign Ministry.

Because of the large number of incidents -- internal estimates cite up to 100 offenses per year -- the Foreign Embassy summoned the Guinea-Bissau ambassador six years ago to ask how German citizens had managed to get ahold of the country's passports. The ambassador insisted during that meeting and several subsequent talks in ensuing years that his consular department had nothing to do with the issuing of the passports. He claimed that everything went through the Foreign Ministry in his home country.

The meetings changed nothing and the police continued to regularly report new offenses, including one in February 2019, when a Guinea-Bissau attaché, a German citizen, parked his black Mercedes sedan in a no-parking zone and blocked a driveway next to a Munich table-dance bar called Queens for half a day.

Then, on the evening of May 7, a woman appeared in the security line at the Frankfurt airport. She had just landed from Marrakesh on Lufthansa flight LH 1333 and at gate A, her hand luggage had to be inspected for a second time. The inspectors found a stack of identity documents.

When federal police sought to examine the documents, Andreas Brandl, a German man who is now 52 years old, intervened. He unexpectedly pulled out a diplomatic passport identifying him as a "special adviser" for Guinea-Bissau. The stack of documents, he claimed, were to be brought to the country's embassy in Berlin.

But a look in the computer revealed that several of the documents were intended for people who were allegedly involved in criminal activities, including drug-related violations, document forgery and insurance fraud.

One of the confiscated diplomatic passports had been issued to the son of a Swiss millionaire whose name was on the German wanted list. In October 2014, he had had his Ferrari 458 blown up by accomplices in front of Colosseum, a high-end brothel in the Bavarian city of Augsburg. The goal was to cash in on the insurance for the 300,000-euro sportscar.

The authorities caught on to the scheme, though, and the young Swiss national was sentenced to 22 months without parole. To this day, however, he has not begun his sentence. It is suspected that he may have wanted to buy a diplomatic passport in order to protect himself from arrest. His lawyer was not available for comment.

No warrant has been issued for Brandl himself, and he and the woman he had been accompanying were both allowed to continue their travels on that day in May.

The embassy of Guinea Bissau learned about the incident and immediately wrote to the German Federal Police requesting the return of 10 confiscated ID papers, including Brandl's diplomatic passport. The "confiscated evidence," it claimed, were authentic and thus the "property of the embassy of the Republic of Guinea-Bissau."

Following the incident at the Frankfurt Airport, the Foreign Ministry in Berlin again contacted the Guinea-Bissau embassy, sending an angry email to the chargé d'affaires saying that a ministry official "would like to urgently speak with you."

At that time, though, the chargé d'affaires was no longer in Germany and the embassy in central Berlin has been largely empty since then, with just a few staff members still on duty there.

Failed State

The building entrance is next to an Asian restaurant and the red, yellow and green national flag in front of the door has become entangled on the mast. The premises on the first floor feel more like a living room than a diplomatic facility. The desk of the acting embassy counsellor is separated off by a partition wall.

The country's current official representative seemed overwhelmed when confronted by the accusations that have been leveled against his government. Unfortunately, he said, he had no time to address them. A staff member promised to provide comment to questions submitted in writing, but no response was received by the time this story went to print.

Corruption, money laundering, political instability: Guinea-Bissau is what one could call a failed state. In the past 20 years, the small country has undergone several coups, a civil war and the assassination of a president. Guinea-Bissau is also seen as an important hub for drug traffic between South America and Europe. Observers have described it as Africa's first "narco-state." In the United Nations development index, the former Portuguese colony is right near the bottom.

The country of 1.8 million inhabitants desperately needs capable government advisers. And there are plenty of indications that Germans like Andreas Brandl do not fall into that category. Years ago, the Foreign Ministry in Berlin refused to accredit Brandl as a diplomat.

The man from Munich had made himself highly unpopular with German investors. Brandl and a companion collected money to make large investments in solar facilities. Financial brokers were full of high praise for the quality of the investments, but they were extremely risky and several of the companies Brandl invested in have since gone bankrupt.

Still, it is striking to note where the companies in question were headquartered. All of them were registered for a time at Kronenstrasse 72 in Berlin, the same building where the embassy of Guinea-Bissau is located.

Brandl was apparently able to convince influential men in the small country of his value and his supposed skills. Documents reveal his rise in Guinea-Bissau's government elite. In his diplomatic passport from January 2019, he is described as a "special adviser to the prime minister," and the document is signed by Guinea-Bissau's then-foreign minister. The document lists Brandl's address as being in the London district of Bayswater.

The building's entry is framed by tall columns and is located just a few minutes from Hyde Park. An grim-looking doorman says that Brandl is probably not at home, but that one could try on the first floor.

A woman in a bathrobe opens the door. Yes, she says, Brandl lives here, but is not currently at home. She takes a piece of paper with DER SPIEGEL's questions and promises to pass them to Brandl but no answers were received by publication and the "special adviser" didn't respond to a request sent via the embassy.

More Suspects

Meanwhile, three German would-be diplomats were recently placed under arrest. They include Stephan Welk, the man who briefly stood in the spotlight in 2018 because of Boris Becker's supposed immunity.

His resume is dazzling: According to a biography he has posted online, he was not only a "special adviser" to the governments of Guinea-Bissau and São Tomé e Príncipe, but he also claims to hold a Ph.D. in economics from the University of Hamburg and the respected London Business School. But neither of the institutions say they are aware of this.

Nevertheless, Welk has held lectures with titles such as "Diplomacy Between Statecraft and Social Science" and told students in Kiev things like: "Understanding diplomacy is a little bit like understanding women. It's something that's really not easy." Towards the end of his lecture, which can be seen on YouTube, Welk tackles the subject of corruption. He says it is always a "different point of view" and says there are, for example, African officials willing to issue diplomatic papers for 500,000 euros to people who value the ability to travel freely.

Sitting behind bars is not a new experience for Welk. In 2003, a Hamburg court sentenced him to a jail term of four years for fraud related to dubious real-estate transactions among other offenses. Starting in 2009, Welk was once again in court, this time in Dresden, where he was sentenced to an additional four years in jail for fraud, a delayed insolvency filing, the forgery of documents and attempted embezzlement and breach of trust. The damages amounted to about 450,000 euros. Part of the money -- 80,000 euros -- was supposedly meant for the procurement of a diplomatic passport from the African country of Liberia, according to Dresden prosecutors.

Four days before Welk was arrested in late August, the police arrested an additional suspect at a gas station in southwestern Bavaria: Mario Daser, the "attaché for culture and sport" of the Guinea-Bissau embassy.

The 30-year-old C-list celebrity is called "Super Mario" by his fans, though less generous observers call him "Disaster Daser." Daser grew up in a rough neighborhood of Munich, where he ended up behind bars for taking part in fights. He then got involved in boxing, initially participating in exhibition fights in beer tents before turning professional. He married the granddaughter of a gravel-plant owner and became a businessman himself. The tabloids wrote that he had gone from jail to "self-made millionaire." Daser posed in front of a Lamborghini Aventador with winged doors and showed journalists his 200-square-meter loft.