Re: Prior art not that important
"Yeah, but in the US they have granted patents on perpetual motion machines.. so i don't think a great deal of checking goes into these."
Have you actually seen any patents granted for one? Perpetual motion machines are actually an interesting exception in US patents, because they're considered so self-evidently stupid that they're the only claim requiring an actual working model be presented before a patent is granted (mainly due to a flood of such applications at one point). No other claim has any requirement to be physically possible, let alone to provide evidence you've actually done it. There are still plenty of crackpot patent applications that are effectively claiming to produce free energy, cold fusion being a common favourite, but they're always very careful to never say anything about perpetual motion or free energy because that would guarantee they'd be immediately thrown out.