Agenda has been exploring the mysterious world of international salt trading, via Edinburgh's Court of Session where National Gritting Services v Scottish Ministers is being heard.

The case, before Lord Woolman, is being pursued by Portsmouth salt trader NGS, which is alleging that Transport Scotland bypassed the proper procurement processes, buying from favoured partners when stockpiling 30,000 tonnes of salt following the disastrous winter of 2009-10. Not only was it against European law to exclude them, NGS contends, but it saddled the taxpayer with unnecessarily high costs for a commodity that it and others could have supplied more cheaply.

In a marathon session on the witness stand on Thursday, poor David Hamilton, Transport Scotland's national network manager of trunk roads, was put through the wringer by NGS's counsel, Aidan O'Neill QC, on the procedures that TS followed - and those it didn't follow.

Hamilton was pressed to answer why Transport Scotland seemed to ignore repeated credible offers of salt at a reasonable price from reputable suppliers in good time for the next winter, instead choosing to deal with accustomed suppliers outside the Scotland Excel procurement process, at higher prices than those set by that framework.

He looked no more comfortable explaining Transport Scotland's mechanisms seemingly designed for avoiding procurement "governance issues", and its obtaining salt indirectly through Transport Scotland's arms-length operating firm, Bear Scotland. The court was read an email from the Scottish Government's head of maintenance, Graham Edmond, saying "If asked, this [salt] will be procured through Bear" - an instruction Hamilton was not able to explain.

Apart from exposing an egregious lack of bureaucratic expertise in what Hamilton called "winter matters" - including apparent ignorance of the so-called "accelerated restricted procedure" that would have allowed them to obtain salt in time for the next winter - the case offers a rare glimpse of the functioning of Scottish Government.

This included some tantalising hints of the influence of the First Minister, even over something as mundane as salt procurement.

Scottish Government head of procurement Alastair Merrill seems to have participated in devising the method of procuring by third party, according to a pompous email from him cited by O'Neill, which said that Salmond "expects everyone to be holding hands on this" [ie, he wants complete agreement in the method of salt procurement].

More about this political oversight will be heard next week.