This past weekend I did a bit of a lengthy drive (from Portsmouth in
Hampshire, to North Somerset, going via Cheddar Gorge). Everything was fine
until I'd almost reached the destination when I braked on reaching a narrow
bridge.

Although the brake pedal was the normal action, it suddenly made a noise
like I'd got 'gravel' in the brakes or under the pedal and the pedal
stopped at about half it's travel movement, with no brakes.
Initial panic over (I was only going slowly and there was no traffic) I
tried again and all appeared to work normally, with the pedal movement
normal and normal braking resumed. I drove on carefully.

A couple of miles later the same thing happened again - sort of crunching
noise/sensation through the pedal, pedal movement restricted and loss of
brakes.

On reaching the destination I checked all the fluids and visual check of
brakes (as much as you can see without removing wheels etc) and everything
appeared to be ok. Nothing leaking and fluid levels ok. I did a few
emergency stops in the carpark and only managed to reproduce the problem
once out of about 5 or six braking experiments.

I left it for the weekend, then gave another visual inspection before
driving all the way home again on Sunday (yesterday). Driving home (about 3
hours, averaging 50-60mph) the brakes were fine and there was no repetition
of the problem - although I was more aware of it so was driving 'carefully'.

I'm wondering if possibly the long drive down there had heated things up
and made a latent problem somewhere more apparent, or possibly the drive
through Cheddar/Mendips put more strain on something - although I do always
tend to use the gears appropriately for steep inclines so the brakes hadn't
had excessive use during the journey.

Does anyone have any ideas where the problem may lie - before I start
taking things apart, or book it into a garage for a once over?
It's a 1997 Discovery TDi ES.

TIA. cheers,
Paul