You will be surprised that the line managers will have unlimited power (veto) against their staff. They basically have full control of the fate of individual while working in the company in term of career progression and performance review. The single line manager (only an individual that your report to) will have absolute power to decide how much bonus you will get, decide if you got any promotion or not. Basically, he/she can control your whole career progression in Shell. Due to this authority given, some line managers abuse it and becomes the little Napoleon in the company and they basically can do whatever they want and please do not expect that HR will be on your side if you complaint about it.
Many staff in Shell got promoted based on favoritism rather than pure merit. Most of the staff who are less competence but know how to play office politics and be in the right crowd get promoted faster based on corridor talk.. This staff also normally cleverly able to make themselves visible by been outspoken and keep highlighting their simple milestone and sometimes useless achievement as great as Mount Everest. Unfortunately, most of the time, they are academically and technically handicapped with poor time and goal management but very good at manipulating facts and figures.
You will be surprised on how the promotion process and career progression works in Shell. You can be doing something of low impact and of no value in other companies but you can easily get good performance review and promotion. The most important things to do is you just need to have good relationship with your line manager, play office politics and about be really outspoken about your little achievement plus stepping on other people's head.
Highly competence staff with have good personality and leadership quality normally is left in the dark. This is simply because they rarely talk arrogantly to announce their excellent achievement and all the great milestones they have achieve for the company. They are rather the quiet person that do the real work in Shell. I have see many worst case scenario happened to these staff when their line manager takes the full credit of these smart and hard working individuals without sharing the glory with them because the line manager are selfish and care only about their career and afraid that more competence staff to take the spotlight.
Many highly competence staff with excellent management skill left the company out of frustration. This lead he company with many staff that are only outspoken, poor time and goal management but sound really good in-front of higher management. They will continue to manipulate facts and figure to climb up the corporate leader as fast as they came while "killing' the good one.