Defender 90, electrical fault

hi guys, occasionally when I go out to start my 2007 defender there is no power whatsoever, like battery totally flat, wait a couple of minutes then try again and it's just like nothing is wrong. Also a couple of times while I've been driving all power goes engine cuts out for a split second, stereo cuts out, then all comes on again. Any ideas?

Bad battery connection, bad earth, internally broken battery cable. As it's an 07 Defender I'd also check the ECU and engine management stuff for poor connections, broken fittings etc.

Thanks for the reply, I'll check these things out.