Following on from my post a few mins ago, here's just one example, now imagine scaling this scenario up across the UK. I know someone who works in the NHS in an administrative role. They earn ~£40k pa. In the department within which they work, the management identified a requirement for someone with an additional skillset. The person I know already dabbled in this area as part of their role and suggested to the management 'can I not receive some additional training and absorb the additional task?' In short the management decided 'no' and employed another person on ~£40k pa. I have no reason to disbelieve him, the person I know is adamant they could have absorbed what this entirely new role is doing.
This happens time and time again and I don't doubt local councils are the same. Of course there will be times when an additional member of the team 'is' required, no one would deny that. However I've heard of more than a few real life scenarios as per the above.