Perhaps the ruthless nature of the Perisher can be summed up in one instance.
In 1942, Lt Peter Roberts and PO Tom Gould of HM Submarine Thrasher was each awarded the VC for disposing of a bomb which had lodged beneath the gratings on their submarine casing. This was danagerous of itself but if the sub had been forced to submerge in a hurry they would have been trapped.
Peter Roberts was sent on his Perisher and his VC was announced during the course. The following day he failed the course and was taken off submarines for good. No concessions, no second chances, no extra coaching - endex!
Roberts was also awarded a DSC and in later life served in the RNXS in (I think) Plymouth working the support vessels used by the navy in and around harbours etc. He died in about 1979 when only early '60s.
Old Duffer