The basic problem with public funding of our ferries is that no government (including the one in which Tavish Scott was transport minister) has ever understood that all of the Scottish ferries we're talking about are 'internal' services, by definition (Scotland's ferries: geographic discrimination or good value for a lot of money? SN, 19/10/2017).
The only 'external' ferries in Scotland are those to Northern Ireland - and the boats that once upon a time ran from Lerwick to Denmark and from Rosyth to Zeebrugge.
The Aberdeen-Lerwick route joins the A90 in Aberdeen to the A970 in Lerwick. In that way it is no different from the Uig-Stornoway crossing, which also links two 'A' class roads. So why are they financed differently?
This is something that Mr Scott and all of his successors have never explained and cannot justify.
The only logical and consistent policy is to treat all trunk ferry routes as if they were trunk roads or bridges and make their funding a central government responsibility. That would include the ferries to Unst, Yell and Whalsay.
There is nothing to stop the SIC continuing to operate these routes, and the ferries to smaller islands, but the money must come from government, as long as there is what Europe calls "market failure", i.e. no commercial operator can make a profit at fares the public can afford.
Longer routes will obviously need bigger subsidies but the yardstick for setting fares must always be affordability for a family on the living wage.
I hope the SNP Government will see the sense of this. Meanwhile Mr Pot should stop criticising Mr Kettle for errors he made himself while in office.