A jury was told by a Nigerian market trader who was allegedly trafficked to London that he was shocked to learn that he would need a kidney transplant.
For legal reasons, the man who cannot be identified said he believed he was traveling to the UK to find employment.
Nigerian politician Ike Ekweremadu, 60, has denied violating the laws against modern slavery at the Old Bailey.
The 21-year-old is alleged to have been brought to the UK so that he could donate his kidney to his daughter Sonia.
Additionally, his wife Beatrice, 56, daughter Sonia, 25, and friend Dr. Obina Obeta, 50, deny conspiring to set up or facilitate the young man's travel to Britain with the intention of exploiting him.
In order to locate a donor in Nigeria and set up the kidney transplant in Britain, the prosecution alleges that Mr. Ekweremadu paid middlemen thousands of pounds.
Jurors were informed that the alleged victim claimed she was "controlled" and instructed to fabricate a family connection to the Ekweremadu family prior to a consultation at the Royal Free Hospital in north London in February 2022.
The doctor told him he was there for a kidney transplant, and the patient was reportedly "shocked" to hear this.
"When he told me about that, I started crying. I informed him that I had no knowledge of a kidney transplant, the court was told.
Two Royal Free doctors disagreed, stating that the transplant should not be performed because of the patient's young age and apparent lack of knowledge of the procedure.
The Nigerian testified to the jury over a video link that he was raised in a remote village without running water or electricity.
He relocated to Lagos at the age of 15 to work for an uncle selling cell phone accessories in a market. He was given the chance to visit London six years later by Dr. Obeta, the defendant who the prosecution has referred to as Mr. Ekweremadu's "fixer.".
The alleged victim of trafficking claimed, "The first day that he called me, all he told me was it was about work.".
"He asked me to refrain from telling people I'm visiting the UK. ".
He flew to London after being granted a passport and visa, according to evidence presented in court. He was instructed to "dress up" before meeting a woman there who he later identified in court as Sonia Ekweremadu.
Jurors were informed that Ms. Ekweremadu has a serious kidney condition that calls for dialysis and a transplant.
They were all captured in a photograph. The purpose of this, the jury has been informed, was to fabricate a photographic "back story" suggesting that they were acquainted.
Despite the decision to forego the transplant, the jury was informed that the alleged victim testified that he had subsequently been examined by two other unnamed doctors at the residence of Dr. Obeta, whom he also accused of making him work as a "houseboy" and failing to pay him.
After leaving the house, he walked through London for two days while rough sleeping, according to evidence presented in court.
The cold was too much, he finally said. That day, the cold nearly killed me. Because of this, I was powerless.
He entered a Staines police station on foot, starting the police investigation that resulted in this trial.
The trial is still going on as Dr. Obina Obeta's defense attorney has started his cross-examination.