I believe I heard/read somewhere that when the first franchise was let Belper got assurances that the then current peaktime commuter services to Sheffield (one service Belper-Sheffield in the morning and one service Sheffield-Belper return in the afternoon) would be kept. However what got put in the specification by mistake was one service a day not one service each way a day. However this might be urban myth.
What is true is that the morning Belper-Sheffield service has been there for some time but the return Sheffield-Belper service is new for this timetable change.
If you look at the timetable it makes a hell of a difference. The direct trains take half an hour to/from Sheffield while via Derby doubles this to an hour from having to travel the wrong direction for 10mins and then change.
The local friends group have been campaigning for this for some years. On thier
website you can download their arguments/research for it which they've submitted to the relevant authorities.
Direct link to the document
It is not clear that their campaign has directly led to this service as they've only just submitted it as their aim is to get into the next franchise specification. On the other hand EMT have been being lobbied about it for some time and granted permission for surveys to be conducted on their trains so did know about it.
Although this new service is not yet a franchise commitment it presumably demonstrates there is no operational impediment in terms of driver/train manager training or rolling stock with adding this stop.
I believe the reluctance to introduce the stop was due to it being a London bound train and the authorities worrying it would cause every tiny village to demand their own direct train to London when in fact it is aimed at developing the regional commuter market from Belper and catchment to Chesterfield and Sheffield.
However because these are London services they are generally most busy in the section between London and Leicester, less busy Leicester to Derby and least busy in the Derby to Sheffield section so there should be plenty of seats available. If the cross-country services stopped instead I suspect that wouldn't be the case.
DDB