Following numerous delays, the £150 million facility was eventually set to open last summer before a safety flaw was discovered in its ventilation system just days before the first patients were due to arrive.

Now a review commissioned by NHS Lothian has discovered a “human error” in an environmental matrix spreadsheet with the specifications for air flow in critical care rooms.

Audit firm Grant Thornton found the spreadsheet wrongly stated that the ventilation system had to be able to change the air in critical care areas four times each hour, instead of the required ten.

The auditors stated: “This looks to be, based on our review, human error in copying across the four bedded room generic ventilation criteria into the critical care room detail.”

During the tendering process in 2013, one of the bidders submitted a revised environmental matrix with the correct air changes. However, it failed to raise questions and the independent contractors hired for the project also did not pick up on the oversight.

The mistake was missed in what the auditors described as a “collective failure from the parties involved” in which it was “not possible to identify one single event which resulted in the errors”.

In their overall conclusion, Grant Thornton stated: “Our review identified a collective failure from the parties involved.

“It is not possible to identify one single event which resulted in the errors as there were several contributing events.

“Additionally, there were a series of factors external to NHS Lothian which influenced and shaped the project which were not within the direct control of NHS Lothian. These factors contributed to the complexity.”

An inquiry regarding Queen Elizabeth University Hospital campus in Glasgow and the Royal Hospital for Children and Young People and Department of Clinical Neurosciences in Edinburgh, chaired by Lord Brodie QC PC, began its work earlier this month.