MY 2005 JAGUAR 3.0 S WAS PROCEEDING EASTWARD ON A CITY STREET WITHIN THE 30 MPH SPEED LIMIT WHEN IT BECAME NECESSARY TO MAKE A SUDDEN STOP TO AVOID A CAR STOPPED IN TRAFFIC LANE. BRAKES FAILED TO OPERATE. BRAKE PEDAL WENT TO THE FLOOR WITH NO SLOWING OF VEHICLE AT ALL CAUSING MY CAR TO HIT THE OTHER VEHICLE.