The Duke talks about Goldline, a US gold coin seller. He is not impressed by their value for money:
Always check the spot price of gold before you pay for coins. Only deal with reputable dealers, hopefully whom a personal friend has recommended. You should be able to find gold coins for somewhere between 2-4% over the gold spot price, if you are not fussy about numismatic values or getting the 'latest' issues. (Though this must be tempered by the very high volatility in gold prices, at the moment.)
For instance, when buying UK sovereigns, if you want the 'latest' 2010 mintings, you will probably expect to pay more, but if going for something from 1964 or 1973, you should be in the 2-4% over gold spot range. (At least, in less volatile times.)
UK gold coin buyers should buy sovereigns. As these are still 'legal tender', they do not attract capital gains tax. Though do expect the Glorious Coalition to cut this escape route off from the horrors of being forced to use legal tender paper scrip.
Alas, because of this tax status, you will probably have to pay 'over the odds' at the moment, as every Jack Bull in England is buying sovereigns to try to avoid the Glorious Coalition's imminent rack-up in capital gains tax.
I hope all those conservative party voters out there are glad who they voted for.