(18 Aug 2013, 8:54 pm)W179SCU wrote Maybe the N21 will interwork with the 0459 21?
The N21 only operates on early Saturday and Sunday mornings, so on Saturday or Sunday mornings there isn't an 0459 21. There's an 0437 and then an 0529 from Chester on Saturday, and on Sunday it's 0437 and then 0554. So there's a considerable in time on both days between when the last N21 arrives in Chester, and the next possible 21 that it could work on departs.