While it remains to be seen whether Linda Cook will be handed the chief executive job at Royal Dutch Shell, it is something of a notable moment that she is in the running.

While female petroleum engineers are rare, female chief executives of big international oil companies are even rarer. In fact, Ms Cook, 50, would be the first if she were to replace Jeroen van der Veer when he retires next June.

Ms Cook, who is the director of gas and power, is thought to be a favourite for the post, along with her colleague Malcolm Brinded, the head of exploration, after Peter Voser, Shell's chief financial officer, was reported to have dropped out of the race.

Both Ms Cook and Mr Brinded are Shell lifers, but it is the American who has had more to prove in the long road to Shell's boardroom. Ms Cook has the manner of a good soldier, rarely seen without her armour. Her big break came in 2000 when she was put in charge of gas and power, then a nascent liquefied natural gas (LNG) development and marketing business. She spent a year running Shell Canada, but was hauled back to Europe after the reserves scandal to beef up the top team and was handed back the gas portfolio.

Mr Brinded, 55, has been seen as the more traditional candidate, more welded into Shell's exploration business. However, the exploration side has not distinguished itself over the past decade. Since the reserves scandal, Mr Brinded has worked hard to rebuild its reputation but the upstream business struggles to shine.

By contrast, LNG has been a great success. There are rumours of plans to fold part of the gas business into exploration to reflect the physical links between upstream oil and gas developments. It is unclear which candidate that might benefit and an outside rider is still possible. That is an option that some investors might welcome.