This isn't actually all that secret. It's been published for over 4 years before it even managed a test flight.<p>Having worked in that sector, the interesting shit is always what you haven't heard about.
The challenge for UAV going forward is to operate autonomously. Stealth is useless if its communications with a satellite are obvious, and almost all drones are useless if GPS is jammed. I haven't found any information indicating that the Taranis solves these problems.
Google says this article about it is December 2006.
<a href="http://defense-update.com/products/t/taranis-ucav.htm" rel="nofollow">http://defense-update.com/products/t/taranis-ucav.htm</a>