Offroad-Express

So I was driving to work yesterday in the Sami and it got all dark and gloomy and started raining.. Being a defensive driver I flicked on the headlights.. and everything died for half a second!?
Engine cut, stereo off, dash lights gone - half a second later all back on again and away we go...
Flick lights off and on again - nothing.
Couple more times - nothing.

Leave for a couple of minutes, lights on and it all dies again for half a second.

Any ideas???

I would start by checking the tightness and condition of the battery terminals.
Take them off, wire brush them and reinstall with some Vaseline on them.

there should be a fusable link between the battery and wiring loom , check its not loose or half burnt out .
then I would check all the main earth pionts .

engine to body and harness earth - firewall by the trans tunnel passenger side
battery to body - by battery
battery to engine - by starter motor
inside cab - attached to cross brace , just under dash passenger side .

then check all the fuses / holders are in good condition.
from memory there is another earth by the fuses as well .

if all those are good check the connections on the back of the ignition barrel.

check the battery terminals for any oxidization and give them a wire brush or a bit of a sand and see if that helps

Id also check alternator could be delayed at bumping up with load

Awesome, thanks for the pointers guys. Turns out it was a dodgy connection under the rubber sheild on the positive terminal of the battery. All fixed.
Found a couple of iffy grond connections as well, so i'll get them sorted tonight.