Derek Smith sued his employers Muir Construction alleging common law negligence and breaches of various workplace regulations following the incident in June 20012.

However, he was diagnosed with pre- and post-traumatic amnesia, meaning he had “no recollection of the accident” and “no memory of how it happened”.

After “piecing together what probably happened”, a judge in the Court of Session Outer House ruled that the pursuer had fallen from a ladder and that the defenders were liable.

Lord Glennie also held that on the evidence, there was “no basis for a finding of contributory negligence”.

On behalf of the defenders, it was submitted that since it was for the pursuer to prove his case on the balance of probabilities, in the circumstances he could prove neither the mechanism of the accident nor its cause and that therefore his claim had to fail.

While the court could draw inferences from the evidence laid before it, it could not “speculate” and in this case the evidence was “simply insufficient” to enable the court to draw any inferences as to mechanism or cause, it was argued.

Lord Glennie agreed with that approach but disagreed with the conclusion, saying that there was “direct evidence” which made it possible to “piece together with some confidence what probably happened and how it happened”.

The court heard that the pursuer and a colleague Steve Stuart were employed by the defenders on a construction site at the former St Bernard’s school in Stockbridge, Edinburgh, which was being converted into residential units with the new build of garages, flats and a three storey townhouse.

At the time of the accident the pursuer was laying the chipboard floor on the ground floor of the townhouse, the first and second floors having been made wind and watertight.

He and Mr Stuart had been issued with a “handle” capable of opening the doors and windows, but they had left on the first floor of the house.

The pursuer decided to go up a ladder to get it as he needed it to open the French doors in order to get the flooring to fit properly.

Shortly after the pursuer had told him that he was going to go upstairs to get the handle, Mr Stuart - who was within earshot but out of sight - heard a crash. He ran through to find the pursuer lying face down under the stairwell opening with the ladder beside him.

Lord Glennie said: “On balance of probabilities, therefore, I find that the pursuer fell when climbing the ladder to the first floor, and that the cause of this fall was probably that the ladder, being unsecured and placed on the new slidy chipboard floor, simply slipped.”

On behalf of the pursuer it was submitted that in the circumstances found to be proved the regulations imposed liability on the defenders.

The stairwell had been left open after scaffolding had been removed and the ladder was placed on the first floor in such a way that it could be reached from the ground floor, but neither the pursuer nor his colleague were told, either orally or in writing, that they were not to go back up to the floor above.

In those circumstances the opening and the ladder had to be regarded as part of the workplace and means of access from one level to another and the existence of an unsecured ladder on a slippery floor as a means of access was a “clear breach” of the regulations.

For the defenders it was argued that the first floor was effectively “out of bounds” as they had provided no access to the first floor and there was no requirement or need on the part of the joiners to get access to it.

The ladder was not intended for use to gain access to the first floor and the accident was caused solely by the fault of the pursuer who had gone up the ladder for his own purposes on a “frolic of his own”.

However, the judge dismissed that argument, ruling that the defenders had breached workplace regulations, though he rejected the common law case.

Delivering his opinion, Lord Glennie said: “The risk of someone using the ladder to gain access to the first floor was clearly foreseeable, as was the risk of an unsecured ladder slipping. Yet there was no evidence that any risk assessment had been carried out. There was no attempt to prevent the ladder being used, either by removing it, blocking up the opening or issuing written or oral warnings or instructions. The first floor remained part of the workplace, despite the work there being for a time complete, and the opening and the ladder provided a means of access from one level to another.

“If the defenders had not wanted access to be taken in this way they should have closed it off or, at least, since there were only two people working there, have given clear oral or written instructions to them that they were not to use it. They did not do that. It is not sufficient simply to rely upon the experience of the workforce to know not to do something. That line of argument, if accepted, would emasculate the regulations. Accordingly, I find liability established.”