  We prove a `Weierstrass Preparation Theorem' and develop an explicit descent
formalism in the context of Whitehead groups of non-commutative Iwasawa
algebras. We use these results to describe the precise connection between the
main conjecture of non-commutative Iwasawa theory (in the sense of Coates,
Fukaya, Kato, Sujatha and Venjakob) and the equivariant Tamagawa number
conjecture. The latter result is both a converse to a theorem of Fukaya and
Kato and also provides an important means of deriving explicit consequences of
the main conjecture.
