Land Rover Repair: Brake Failure, land rover discovery, vacuum servo

Question
1996 Land Rover Discovery SE7 4.0 Gasoline

My teenage son's disco has twice had brake failure over the last few months.  It happened today as he was coming to the end of our street (luckily he was only going 25mph & he knew to throw on the emergency brake) and he was unable to stop.  The brakes were hard not soft.  We are wondering if this could be air in the lines, a vacuum issue, or what???  You were a big help to us with our last inquiry about a window ECU so we are hoping you can shed some light on this new problem!!!

Answer
Yes it's only can be vacuum problem. Maybe the vacuum hose has broken somewhere and the vacuum cannot go to the vacuum servo drum. Or the hose is loosen.

Third variation is the vacuum drum is flown the vacuum.

So, if the pedal was hard to push, than It was vacuum problem I'm sure.