After a normal landing the aircraft suffered a complete brake failure. To avoid overrunning the end of the runway the pilot steered the aircraft, at low speed, into the grass at the side of the runway. The incident was caused by the failure of a brazed joint, between a pipe and a fitting within the left brake system. Examination of the pipe and fitting revealed the presence of a contaminant within the brazed joint which had resulted in the eventual failure of the joint. There was no evidence of repair to the brazed joint; therefore, it was concluded that the contamination of the joint had occurred during the original manufacturing process. The service life of the unit could not be determined and analysis of AAIB records did not reveal any similar events on the Jet Provost fleet.