...potentially by a panicking contractor, if reports are to be believed.
BA IT systems failure: Uninterruptible Power Supply was interrupted ? The Register
Bill Francis, Head of Group IT at BA's owner International Airlines Group (IAG), has sent an email to staff saying an investigation so far had found that an Uninterruptible Power Supply to a core data centre at Heathrow was over-ridden on Saturday morning. He said: "This resulted in the total immediate loss of power to the facility, bypassing the backup generators and batteries. This in turn meant that the controlled contingency migration to other facilities could not be applied. "After a few minutes of this shutdown of power, it was turned back on in an unplanned and uncontrolled fashion, which created physical damage to the system, and significantly exacerbated the problem.
The rest of the article makes interesting reading.