As a UK citizen, it stuns me that one-in-thirty pound coins is a fake because a) i can't imagine how it's possibly worth it b) out of the thousands of pound coins i must have handled, I've never spotted a fake - they must be very good. Still, the new coin certainly looks nice!
Let's say you're one of three (or five) major creators/distributors of said coin. a third (or fifth, or whatever) of a thirtieth of all the pound coins in circulation doesn't seem worth it to you?
> As of March 2014 there were an estimated 1,553 million £1 coins in circulation
A fifth of that would be ~311 million pounds.
Let's say you're one of fifty or 500 counterfeiting rings, that's still £31 or £3.1 million. Even if the process for counterfeiting cost a million pounds to acquire (probably much less), it'd still be £1M pure profit. The numbers for both cost and slice of the pie probably scale down to a bunch of small-time counterfeiters, but the margin is definitely there.