This report is from this week's CNBC's UK Exchange newsletter. Like what you see? You can subscribe here. It is just over three years since Wael Sawan succeeded Ben van Beurden as chief executive of Shell. While there has been much background noise, not least about a possible takeover bid for BP, a less remarked-upon aspect of Sawan's time at the helm to date is just how often the oil major has beaten expectations on results day. In five of the last eight quarters, Shell has reported better-