THE referendum campaign on whether the UK should leave the European Union will not be viewed by historians as this country’s finest moment.

Blatant untruths were told by Brexiteers about the benefits of leaving the EU and the official campaign broke the rules on spending.

Much of the campaign was also played out against the backdrop of a foul appeal to voters’ worst instincts on immigration.

David Cameron pulled his punches on his Brexit colleagues, Jeremy Corbyn was nowhere to be seen, and the Remain side was a shambles. All in all, it was a horror show.

One of the most mysterious aspects of the campaign was over-funding. As has been confirmed, the little-known Constitutional Research Council, chaired by former Scottish Tory candidate Richard Cook, donated around £435,000 to the Democratic Unionist Party.

However, most of the money was spent on an advert in a newspaper not sold in Ulster, which is odd given that the donation was made to a party in Northern Ireland.

What we know is that the CRC was formed in the year of the Scottish independence referendum and exists to fund pro-Union causes.

However, no other details have been offered by Cook. We do not know who sits on the CRC executive committee, or how much it has raised. Crucially, we do not know who gave the CRC the £435,000.

Cook is perfectly entitled within the law to say nothing about the CRC – he does not have to answer any questions – but the donation raises important issues about transparency and how weak our laws are.

SNP MP Brendan O’Hara’s call for Cook to be invited to speak to MPs before a select committee is therefore to be welcomed.

Cook should be asked questions about this secretive organisation and help shine a light on to one of the more bizarre aspects of the Brexit campaign.