Yes, it was Rivlin who'd suggested it was a trick of the light so those concerned so it was passed off as such and Bews had agreed. When JB was being questioned he thought he might have been asked about the " movement " via the window also but wasn't. So JB had obviously fully expected there to have been chapter and verse on this but it never happened.
I'd have butted in if I'd been JB and told them all to hang on----how gormless was he ? 
Well I guess the prosecution could hardly say they called in armed police because they thought they saw movement in the window, if I had been Rivlin I would have insisted on seeing Bews situation report, the trial would have come to a sudden end!