About ten years ago, I was doing an "admin" role and when I joined the company I was paid around £12/13k, when I left that team about five years later, I was on £19k.
The same role was advertised earlier this year for £17k, so five years after I left it on £19k. I was surprised by this. It was and still is quite a technical role with lots of knowledge required about the business area.
In comparison, my employer is a "living wage employer", which no one is paid less than £7.83 (assuming over 25), so for a 35 hour week - roughly around £14k, if it's a 40 hour week like most that's just over £16k.
So they expect someone with the required skills and knowledge to work for slightly more than LW?
I think the problem is some employers are finding it tough to pay for the NMW increases so they don't increase the salaries of people already above this. My DP had a skilled qualification at his old job which historically always meant anyone with this qualification was paid slightly more than those without it - when the NMW kept increasing, the employer had to put those wages up, but didn't increase anyone else's so eventually the staff who were qualified were being paid the same as those who didn't have the qualification - which meant lots of those with the qualification just left.
In other example, I am currently on £29k after five years in my job (which started at £21k), we are now advertising for a vacancy at the grade below me, when I started the grade below started at £19k, they are advertising at £16.5k 