Sorry, my routing guide knowledge is near zero...
Is a London Terminals - Derby Any Permitted super off peak return valid via Grantham?
I'm likely to have an outward journey from St Pancras via Nottingham, and return via Grantham into London Kings Cross.
Thanks in advance!
No, London (LON) to Derby (DBY) is only valid via Rugby or via Kettering.
LON to Nottingham (NOT) is, however, valid via Grantham (GRA) (as well as via Kettering).
Both DBY and NOT are valid via the other to get to LON (i.e. you can do LON-DBY via NOT or LON-NOT via DBY).
So you can't quite do what you're proposing on a single ticket to either DBY or NOT, because to go LON-DBY via NOT you have to get a DBY ticket, but to return via GRA you need a NOT ticket.
A ticket to Chesterfield is slightly more expensive but would definitely permit you to do what you're proposing in one ticket.
Depending on what kind of ticket you're after (Super Off-Peak etc.) it may be cheaper than buying a LON-NOT ticket for the validity via GRA, and then buying a NOT-DBY return to cover you between those two.
(You'd need the extra NOT-DBY ticket because if you used your LON-NOT return portion to cover you from NOT-DBY on the outward journey, you couldn't then use it to return to LON via GRA, because you have to stick with a permitted route once you choose it for a given ticket portion.)
