I recently operated JNB-LHR, incurring unexplained extra burn en-route, which made our arrival fuel only a little over our company minimum reserve. Sometimes these things even themselves out over time, but nothing had changed by 1.30 to ETA. Warned company and asked them to pre-warn ATC that we would only have once round BIG before needing to make approach. Unfortunately, message not received by relevant controller, so first they knew of our fuel state was as we arrived at BIG. Didn't get vectored off straightaway, second time over BIG declared PAN as considered potential for landing below final reserve. Expeditious approach and landing. Phoned ATC afterwards, agreed only lesson to be learned was to ensure on first contact with UK ATC that they are fully aware of situation. Job done, these things happen, that's why there are procedures.
