One thing that I have noticed over the past year, is that it is getting increasingly difficult to quickly check card account statements by just casting an eye for an oddities. Buried amongst the endless supermarket, filling station, newsagent, bar, coffee shop, A*****n, etc, etc. purchases, there could be anything. Combined with a tendancy for companies to use a bank name that it totally different from what you would expect, and it sometimes takes a bit of digging before I can work out where a sum was spent. If anyone asked (which they won't), I doubt I could legitimately identify everything on a statement, and could easily make up some credible answer if required.
Clearly, if you use a CC to pay for a high priced duo, or for an SP who uses an explicit business name, then it will stand out like a sore thumb. However, for the odd 15-30 minute, reasonably priced punt, to a sensible account name, then it will disappear amongst the background noise. It all depends on how controlling, suspicious and investigative your OH is.