Yep not great news for such a high profile family, and lots of lost history, but luckily no personal injury....
But how can you not remember if you left a battery charging and overnight!?!
IF a battery is not in use or being charged then only a wiring fault could start this surley????
Once a fire is started then no battery is safe and the 'bangs' heard were probably the other batts going off.
Either way think mine will living in the ammo box asap