Questions have been asked as to whether concerns were raised about the conduct of Dr Michael Watt at his annual reviews - or at the time of his last medical licence renewal by the GMC.
Last week, 2,500 patients across Northern Ireland received letters from the Belfast Trust telling them that their cases were to be subject to an urgent review, after concerns were raised about Hillsborough neurologist Dr Watt's performance.
It followed an independent investigation by the Royal College of Physicians. Dr Watt was employed by the Belfast Trust for just over 20 years.
The Belfast Trust has said that "concerns were raised by doctors at the end of 2016 (December) and immediately patient safety measures were put in place which included restrictions on aspects of Dr Watt's practice".
However, it has since emerged that complaints about Dr Watt were made as far back as 2011.
Despite this, he was suspended from clinical duties in June 2017. He is still an employee of the Belfast Trust, and remains on full pay.
Under GMC guidelines, doctors must undertake an annual appraisal which complies with GMC guidance and covers the whole of their practice.
As part of the process, doctors need to maintain a portfolio of supporting information, which includes evidence of continuing professional development, quality improvement activity, significant events, feedback from patients and colleagues, and complaints.
Every five years, Responsible Officers make a recommendation to either revalidate, defer or non-engagement each doctor's medical licence.
In responses to this newspaper, the Belfast Trust failed to clarify the dates of Dr Watt's last annual appraisal, or when his licence was last revalidated by the GMC.
A doctor with several decades of experience queried whether any concerns had been raised during the consultant's annual reviews, or at the time of his last medical licence renewal by the GMC.
He also raised concerns over the Responsible Officer at the Belfast Trust who had "signed off" on Dr Watt's medical licence revalidation.
"Doctors undergo annual appraisals, and after five years, if they are satisfactory, they are signed off by the Responsible Officer, who recommends that their medical licence be revalidated by the General Medical Council," the medic explained.
"It's a 360 degree appraisal by a doctor in their speciality, as well as qualitative support from patients and continuous professional development.
"You need five good appraisals for the Responsible Officer to sign it off.
"I am concerned at the length of time that it has taken the Royal to do something about this.
"If the first concerns were raised in 2011, as some patients are claiming, then Dr Watt could have gone through numerous annual appraisals and had his medical licence renewed at least once since.
"The Royal must have been intimately involved in ensuring he had a medical licence."
He added: "Any concerns should have been looked at as part of the annual appraisal and the Responsible Officer at the hospital should have reviewed the previous five years when it came to revalidation.
"Someone in neurology at the Royal must have done the appraisals, and someone in the management team at the Royal must have signed off.
"I would like to know, who did sign off on Dr Watt?"
The doctor said he believed there was a need for a "sworn enquiry" in front of Sir John O'Hara, who led the hyponatremia enquiry.
Dr Watt is currently listed on the GMC register as "registered with a licence to practise" and "on the Specialist Register".
The Belfast Trust says that the neurologist at the centre of the major patient recall had his appraisals "up to date" and his medical licence was successfully "revalidated" by the General Medical Council (GMC).
A Belfast Trust spokeswoman said that Dr Watt is "restricted from undertaking clinical duties both in the NHS and private sector", and that the Trust is "liaising with the GMC".
She added: "Belfast Trust, as with other trusts, has a system for appraisals for all doctors, which complies with GMC and departmental guidance.
"On a five-yearly basis the trust is required to make recommendations to the GMC as to whether individual doctors should be revalidated to continue practicing as doctors".
She said that Dr Watt "has been revalidated and his appraisals are up to date".
"Recalling patients is not a decision we take lightly and it is important to be sure of the facts to avoid unnecessary anxiety for patients," she continued.
"Acting earlier than we did would have been premature, as this would have been in advance of Royal College of Physicians findings.
"We continue to work closely with the Department of Health, the General Medical Council and the Royal College of Physicians whilst this review is ongoing."
Meanwhile, the Belfast Trust revealed that the two locum consultants who have been employed to attend to Dr Watt's recalled patients were recruited "via an agency".
Currently, the trust's patients must wait one year for an urgent appointment and four years for a routine appointment with a consultant neurologist.
The spokesperson continued: "We recognise that waiting times are longer than they should be, however the demand for neurology service exceeds capacity.
"The recall of patients will not impact any patient currently waiting to be seen.
"The clinics for the recall are additional clinics run by both trust consultants and we have asked two healthcare providers from the independent sector to assist this patient review".
The trust said that "whilst there will be a cost associated we will not know the full extent until the recall has been completed." It added: "This recall is not about cost, it is about patients."