A lot of people get the title of theTrade Descriptions Act wrong.
It was probably one of the longest-lasting unamended bits of legislation on the statute book. [It is dated 1968.] The section about misleading prices was repealed by the Consumer Protection Act 1987 (so it lasted nearly 20 years without amendment). It has recently (May 2008) been almost totally revoked by the Consumer Protection from Unfair Trading Regulations 2008 - so about 40 years for the rest of it.
I recall that the advert says how long the elapsed time is. If your penny does not come clean after that time (give or take 50%, say, you cannot quibble about a few seconds either way) then you could take your evidence to your local Trading Standards Department. They, unfortunately, will probably not be very interested. You could also take it up with the ASA. They have no power to punish the advertisers, but they can get the adverts stopped.