300tdi alarm problem?!

Could anyone tell me what way i can disconnect the battery on my 1996 disco 300tdi auto without setting off the alarm. I would need to get some welding done soon, and disconnecting the battery is the first step.
Don't know if anyone out there came across this problem, but there must be a pretty obvious answer to this one.

Either check in the manual on the method to do it or just unplug the alarm. Either way is simple

I even unplugged the alarm speaker/horn thing under the bonnet while my alarm was going off and it still wouldn't stop. The alarm must have an alternative source of power regardless of the battery??
But, ill look it up in the manual and hopefully ill find the answer to my mystery

to be honest, ive never had the alarm go off on my disco when disconecting the battery, and because it doesnt have an ecu as such, i just use a surge protector over the battery terminals, you realy only need to disconnect the batterys /ecus when tig welding as it works at higher frequences, if you dont have surge protector then disconnect the negative lead and youll be fine,alarm wont go off, unless its aftermarket, even then two ways. turn ignition on then off and disconnect battery within 15 seconds. or lock unlock with the fob then disconnect!

Thank's very much for the handy tricks dollydisco!

Im going to be using a MIG welder which might even be ok but ill try the 'lock, unlock and run quick and disconnect' trick.
As the weather is nice i want to do a attack on my Discovery and get some welding done... MOT in September... loads of time. Nothing too serious but I'm better off dealing with it before it gets worse. Just the two rear chassis to bodywork mounts and one small patch on the boot floor. I mite come across some rust when i pull off the plastic sills though!? And then after that Neutrarust 661... and the whole lot!