Christopher Clark's Sleepwalkers goes into some detail on Grey and his part in the diplomatic mess that blew into a war. He faults Grey for being extremely cagey and reserved, which led others ( Germany especially) to be confused as to what England's positions and commitments actually were, right when clear signals were immensely important.

Clark's larger thesis- that the war was started by a huge miscellany of bungling by many agents- has been criticized for being far too tidy, and that it ignores the territorial gains the Germans must have imagined they would get from the conflict: they had always gained something from their previous conflicts under Bismark and this looked to be another example. But that critique is not so important , when answering your question about Grey.