"I knew that working tired puts the patients at risk and puts myself also at risk, as well for litigation.

"I felt powerless… helpless, you know, constant stress and thinking something could go wrong."

Nuffield Health however claimed that its doctors are offered regular breaks, time off between shifts, and the ability to swap shifts if needed. The company adds that "the health and wellbeing of patients and hospital team members" is its priority.

Augustine was hired out to the Nuffield Health Leeds Hospital from a private company - NES Healthcare. It specialises in employing doctors from overseas, many from Nigeria, and using them as Resident Medical Officers, or RMOs - live-in doctors found mainly in the private sector.

Augustine says he was so excited to be offered a job that he barely looked at the NES contract. In fact it opted him out of legislation that protects UK workers from excessive working hours, the Working Time Directive, and left him vulnerable to a range of punishing salary deductions.

The BMA and the front line lobbying group the Doctors' Association has also given the BBC's File on 4 and Newsnight exclusive access to the findings of a questionnaire put to 188 Resident Medical Officers. Most of the doctors were employed by NES but some were with other employers.

It found that 92% had been recruited from Africa and most - 81% - were from Nigeria. The majority complained about excessive working hours and unfair salary deductions.

While the World Health Organization (WHO) has warned against the "active recruitment" of doctors and nurses from developing countries (mostly in Africa) with severe shortages of medical personnel, the UK government has also incorporated that list into its own code of practice - calling it the "red list". In effect, it makes Nigeria a no-go destination for British medical recruiters.

On how Nigerian doctors are recruited, it was gathered that these doctors take what's called a Professional and Linguistic Assessments Board test - or PLAB 1. The paper is set by the General Medical Council in London and is the first step required by the British medical authorities to secure a licence to work in the UK.

The Nigerian doctors who spoke to the news agency, said they were attracted by the potential of higher salaries and better working conditions. The event was being overseen by staff from the British Council - an organisation sponsored by the Foreign Office.

The GMC also offers the exams in several other red-list countries - Ghana, Sudan, Pakistan and Bangladesh.

Both the GMC and British Council deny they are involved in "active recruitment" and say they're simply helping provide a service for doctors wanting to come to the UK independently - something that is allowed under the guidelines.

In Augustine's case, he was studying for the second part of those PLAB exams in the UK, when he was approached by NES Healthcare and later offered visa sponsorship and a potential job.

While that does appear to have been "active recruitment", NES says it wasn't because it is not a recruitment agency and, as such, only engages with doctors from overseas once they've already committed to practising in the UK. But the Department of Health and Social Care told BBC that the UK code of practice did apply to NES, so the company was in breach of it.

We spoke to several African doctors recruited in this way by NES. They all had similar stories about what the terms and conditions of their contracts meant in reality, once they had been hired out to private UK hospitals.

Another victim who BBC spoke to is Dr Femi Johnson was sent to a different hospital to Augustine. He said he was also expected to work 14 to 16-hour days and then be on call overnight. "I was burnt out," he says. "I was tired, I needed sleep. It's not humanly possible to do that every day for seven days."