Land Rover Repair: 2000 range rover hse 4.6l

Question
please could you enlighten me as to what the problem might be with my brakes.i have an issue when first starting the car that my brakes do not work for about 20 secs. the pedal goes straight to the floor with very little resistance. after about 20 secs or so the brakes work fine. i have no leaks in the system. appreciate your feedback.

Answer
The problem is probably one of three things:
- The pump that builds brake pressure may not be working at first.  It's on the driver fender well and should be audible at startup
- The accumulator ball that holds brake pressure may be discharged.  You know this is happening if you jab the pedal 3-4 times in quick succession and see a brake warning lamp
- The brake master unit may be failing.