I would just like to answer the question you asked Professor Marland earlier about negative advertising. Interestingly enough, studies in the United States have shown there is more information found in negative advertising than in positive advertising. There are more lies in positive advertising than there are in negative. It has something to do with how we understand what is contentious. If you're going to make a contentious claim, you'd better have the evidence to back it up. I just wanted to add that before I answer your question.
On the question about how we archive or store them, I'd refer you to Professor Marland's idea from earlier, which I would endorse fully, that we need to maintain the principle of transparency. In Australia, for example, they not only have the advertising budgets on the website, but they actually have the companies that receive each campaign and the amount. The annual report of the government for advertising is useful, but it doesn't break it down in that much detail. Also, interestingly enough, in the interest of transparency, it comes out 10 months later. The 2016-17 report will come out in January 2018, 10 months later. It's very difficult for opposition members to hold the government to account if they're looking at a historical document.