There are a number of different ways. We have two compliance and monitoring teams and they carry out surveys of potentially problematic areas -- we tend to focus in on sectors or issues where we know there are problems -- and they will look at a large sample of ads and ascertain the compliance rate, but they will also pursue advertisers who have published ads who appear to break the rules.
They will also act on obviously problematic ads which are drawn to our attention, either as a result of complaints we've received, where it would, in our view, be wrong for us to investigate, which might take some time, and allow an ad that is blatantly in breach of the code to carry on appearing, so they might step in and take immediate compliance action there.
They will undertake what we call sector compliance. If the ASA has adjudicated against a company and the company says, not unreasonably, "It's a fair cop but everyone else in my sector is doing exactly the same thing", we take that seriously, it's not right that there shouldn't be a level playing field, and so the monitoring and compliance team may well undertake sector compliance and get in touch with the other companies, draw to their attention the appropriate adjudication and ask them for an assurance that they'll make changes to their ads. Those are some the cases in which we carry out this sort of activity.