So the aircraft were flown unarmed and usually without instruments, whose accidental loss to the enemy would have given away our marginal technological lead.

More than half of incidents involved a malicious insider, with 35 per cent down to accidental loss.

Crucially, she did not give you the option of insuring for accidental loss of unspecified items.

On land the distinction between deliberate and accidental loss led to the concept of a treasure trove.

The vast majority of these finds are casual or accidental losses that in reality do not have any precise archaeological context.