Detail:
  Covers the basic functionality, but does require a customised start.elf
  to function. The vast majority is an entirely new implementation and is
  BSD licenced, but 4% (the Makefile and a handful of simple macros) are
  copied from pre-existing Castle-licenced code, so it lives under the
  "mixed" hierarchy. If other HALs are anything to go by, we'll end up
  having to add more Castle code (at least some C runtime functions) so it's
  probably juast as well.
Admin:
  Code received from Adrian Lees