Hi all,
I'm going up to Sheffield this weekend on Friday evening and returning to STP on Sunday. I'm intending to stay overnight with my brother in Dronfield on Friday. Am I allowed to do this on one ticket? Or do I have to buy the return to Sheffield and additionally a single from Chesterfield/Sheffield to Dronfield?
Break of journey is permitted on the vast majority of walk-up tickets, including the various Any Permitted and via Chesterfield fares from London Terminals to Sheffield. This includes overnight break of journey.
However what you need to bear in mind is the date-wise validity of the ticket. If you buy an Off-Peak or Super Off-Peak Return, the outward portion is only valid for one day. It's only the return portion that is valid for a month. Therefore whilst you could quite legitimately travel up to Sheffield on the Friday, travel down to Dronfield on the Friday night and then continue down to London on the Sunday - you couldn't travel up to Chesterfield on Friday and then continue up to Dronfield on Saturday.
The other factor to bear in mind is the time restrictions that apply on a Super Off-Peak Return - you couldn't take any train from St Pancras between the 15:32 (or 15:35 changing at Nottingham) and 19:02. An Off-Peak Return would be valid at any time from the 09:02 on Fridays (this seems to be a recent change), but would cost considerably more.
You might also be interested to know that there are cheaper tickets valid only on London Northwestern and CrossCountry, i.e. for use from Euston via Tamworth. Some of the connections at Tamworth are very good, meaning the journey time is not much longer than the direct EMR service from St Pancras. The time restrictions are similar, but the fares are considerably cheaper - Off-Peak is £64.90 vs £139.00, Super Off-Peak is £53.90 vs £87.00. The only complicating factor would be that, because you'd be limited to XC between Sheffield and Tamworth, you couldn't stop off at Dronfield (they don't call there). But even if you bought a separate ticket for that bit of your journey, it would still present a considerable saving.