Some apologies are more sincere than others. Take, for example, the case of the angry passenger who wrote to his train company to tell them he had found beetles crawling all over his seat.

"We were appalled to hear about your unpleasant experience," the chief executive wrote back. "We are truly sorry. Nothing like this has ever happened before. We have instigated a thorough review of our cleaning procedures, sent relevant staff for retraining, and will seek to ensure that there is no repetition of this exceptional - but wholly unacceptable - incident."