  This paper classifies the blocks of the cyclotomic Hecke algebras of type
G(r,1,n) over an arbitrary field. Rather than working with the Hecke algebras
directly we work instead with the cyclotomic Schur algebras. The advantage of
these algebras is that the cyclotomic Jantzen sum formula gives an easy
combinatorial characterization of the blocks of the cyclotomic Schur algebras.
We obtain an explicit description of the blocks by analyzing the combinatorics
of `Jantzen equivalence'.
  We remark that a proof of the classification of the blocks of the cyclotomic
Hecke algebras was announced in 1999. Unfortunately, Cox has discovered that
this previous proof is incomplete.
