As this volume demonstrates, at roughly 100 years of age operator theory remains a vibrant and exciting subject area with wide ranging applications. Many of the th papers found here expandon lectures givenat the 15 International Workshop on Operator Theory and Its Applications, held at the University of Newcastle upon th th Tyne from the 12 to the 16 of July 2004. The workshop was attended by close to 150 mathematicians from throughout the world, and is the ?rst IWOTA to be held in the UK. Talks ranged over such subjects as operator spaces and their - plications, invariant subspaces, Kre? ?n space operator theory and its applications, multivariate operator theory and operator model theory, applications of operator theory to function theory, systems theory including inverse scattering, structured matrices, and spectral theory of non-selfadjoint operators, including pseudodi?- ential and singular integral operators. These interests are re?ected in this volume. As with all of the IWOTA proceedings published by Birkh¨ auser Verlag, the - pers presented here have been refereed to the same high standards as those of the journal Integral Equations and Operator Theory. BANACH C* ALGEBRAS H CONTROL HILBERT KREIN OPERATOR THEORY INTERPOLATION VON NEUMANN A few words about the above image which graced the workshop programme and bag. In commuting between home in Hexham and work in Newcastle, I often x Editorial Preface travel by train.