I can only base this off former graduates who have been promoted through the ranks in a relatively short period. From what I've seen and heard it seems like Viva are very supportive of career progression and offering those opportunities when possible. A key part is the individual making their aspirations known to their line-manager and to also seek out those opportunities.
I have heard stories of graduates being promoted not too long after they roll of their graduate program. It takes curiosity, a commitment to learn and initiate to move up the ranks. Viva does an excellent job at providing learning opportunities through their lunch and learn sessions as well as their commercial excellence sessions, which anyone can attend, company-wide. It is very easy to get comfortable and be stuck doing mundane, ad hoc tasks as a grad, but it's up to you to put your hand up and tell your manager that you'd like to get involved in more projects.
I have not been with the company long enough to have a clear picture on what progression looks like - it seems to vary significantly based on the individual. Although the graduate program is rotational - which is great - I do believe there could be more flexibility in tailoring rotation options to your career aspirations.