(link to the job posting here and the supporting PDF here, main text copied below)
Sounds like a fun job to me (as someone who inputs and interprets data in their spare time), and a good way to wrangle your way into a ROC, but the first line of the post sounds like it's for internals only. Would anyone be able to shed some light on this, and what sort of roles would be worth applying from?
Additionally, here's the skills/experience section from the more information PDF:

Sounds like a fun job to me (as someone who inputs and interprets data in their spare time), and a good way to wrangle your way into a ROC, but the first line of the post sounds like it's for internals only. Would anyone be able to shed some light on this, and what sort of roles would be worth applying from?
GTR are recruiting a Delay Attribution Assistant based out of our Rail Operating Centre in Three Bridges
This is a great opportunity for an individual with a proven track record to work for one of the country's busiest and award-winning rail companies.
Please note: the role requires working Early (0600-1400) and Late shifts (1400-2200) including weekends and bank holidays.
Job purpose
To ensure the correct investigation, attribution and reporting of train running delay information.
Key success criteria
• Ensure the prime cause of all incidents are correctly described and coded so that no incidents go un investigated
• Ensure all information fields within an incident are correct and displaying all information
• Adhere to contractual and internal timescales of attribution
• Ensure that the correct responsible manager is allocated to each incident based on prime cause
• Identifying patterns and trends and sharing these with the wider function.
Results area
• Adhere to the Delay Attribution Principle and Rules (DAPR)
• Follow the correct attribution processes within the GTR Internal Attribution Policy
• Communicate effectively with internal and external stakeholders
• Obtain reports to assist with incident investigations.
Additionally, here's the skills/experience section from the more information PDF:

