You have so far failed to pay £25 for a Green Card (insurance confirmation necessary for travelling abroad) which was issued several months ago. You have felt disinclined to offer payment until the insurance brokers asked for the money and intend now to offer only £15, since you were put to considerable inconvenience by the insurance company (for whom the brokers act). They were extremely inefficient, failing to produce the card on time despite adequate notice, and only supplying one eventually at the eleventh hour after you had made several telephone calls and personal visits. What sort of covering letter would you send with the cheque?