The unexplained journey from M2 to M3….how do I get there?

So to add context, I completed my induction in March 2023. I actually began induction way back in 2018 (back when the NQT was a one year process), but I had to have it extended, leading to me taking some time out from teaching before coming back to it a few years later and eventually finishing it last year. As such, I have not followed the pattern that other ECTs have done since the introduction of that system. For example, when I finished my induction, from the next academic year, I was immediately moved up to M2, but of course lost all of that extra ECT time for planning (fair enough), but I learned that ECT second years are also on M2, and still get extra time for planning. This academic year, I (believe) I am still on M2 as I have not had a conversation about pay yet, and I am a mentor to an ECT2, who, if I believe correctly, will be on the same salary as me. It does not seem right that I would be mentoring someone who is getting paid the same as me. Should I be on M3 at this point? How do I approach it with SLT? Do I need to be observed in order to move up the pay scale?

Many thanks!