Like these images :
Actually I'm surprised that the RN even had such a revolutionary concept in mind.
Even though we won't see submarines like that for at least another 50 years, but in the end whats the best hydrodynamic hull for underwater voyage ?
Take a hint at nature, and I'm sure that sooner or later we will see submarines being based on caracteristics of sea mamals (dolphins, whales, etc..), you can't beat nature when we talk environment-efficiency. :p