Looking at advances from Chester to London on the TPE website (several dates in June) and an option comes up on 'show slower routes': "CH & ATW ONLY". However, ticking this box doesn't seem to have any effect on the itineraries returned and in any case no Chiltern & Arriva Trains Wales Only advance fares are offered. I've tried the LM website too, just in case it's a bug on the TPE website. I've tried avoid MKC, via Banbury, destination MYB but nothing seems to work. Even with the box ticked, I'm still offered VT, LM or XC for one or more legs. Any suggestions?