  Long standing data from niobium thin film accelerating cavities will be
revisited and analysed by a modified London model of RF superconductivity.
Firstly, the applicability of this model is explored using data of the BCS
surface resistance and its dependence on the RF magnetic field, temperature and
mean free path. Secondly, the RF losses from trapped magnetic flux are analysed
with regard to their dependence on these same parameters.
