A return ticket that has validity from Micklefield (or, for a wider choice, Leeds) to Bridlington and return from Bridlington to Doncaster would do the trick then.
Micklefield is a member of Leeds group.
Bridlington is a related station to Scarborough and Hull.
Doing a fare comparision, we get:
Micklefield-Bridlington SDS £23.80
Micklefield-Scarborough SDS £25.40, so Scarborough is not an appropriate routeing point.
Micklefield-Hull SDS £19.30
We find that in this case, Hull is the only appropriate routeing point.
The only routeing permission for Leeds Group-Hull is: TP
Map TP only allows travel direct via Selby.
http://www.atoc.org/clientfiles/File/Maps.pdf page 107
So Micklefield won't do.
For Leeds, the fare comparison is
Leeds-Bridlington SDS £23.80
Leeds-Scarborough SDS £25.40, so Scarborough is not an appropriate routeing point.
Leeds-Hull SDS £19.30
So Leeds is in the same boat as Micklefield.
An Off Peak Return (SVR) from somewhere like South Elmsall to Bridlington would work. In fact, an SVR from South Elmsall to Scarborough would probably work, with the return journey being "broken" at Bridlington. I'd need to check the Routeing Guide, and will do and post later.
South Elmsall is a related station to Doncaster, Pontefract, Swinton and Wakefield.
http://www.atoc.org/clientfiles/File/routeing_point_identifier.pdf page 55
The fare comparison test gives:
South Elmsall-Scarborough SDS £25.10
Doncaster-Scarborough SDS £26.20, so Doncaster is not an appropriate routeing point
Pontefract-Scarborough SDS £25.10, so Pontefract is an appropriate routeing point
Swinton-Scarborough SDS £29.70, so Swinton is not an appropriate routeing point
Wakefield-Scarborough SDS £25.10, so Wakefield is an appropriate routeing point
Routeing permissions for Pontefract-Scarborough are LY and NE
http://www.atoc.org/clientfiles/File/permitted_route_identifier.pdf page 768
Map LY allows:
Pontefract-Leeds-York-Scarborough, covering your outward journey
Pontefract-Wakefield-Leeds-York-Scarborough
Pontefract-Leeds-Selby-York-Scarborough
Pontefract-Wakefield-Leeds-Selby-York-Scarborough
http://www.atoc.org/clientfiles/File/Maps.pdf page 70
Map NE allows:
Pontefract-York-Scarborough
http://www.atoc.org/clientfiles/File/Maps.pdf page 81
The only routeing permissions for Wakefield-Scarborough is TP
http://www.atoc.org/clientfiles/File/permitted_route_identifier.pdf page 1039
This allows
Wakefield-Leeds-York-Scarborough
Wakefield-Huddersfield-Leeds-York-Scarborough
Wakefield-Pontefract-Leeds-York-Scarborough
http://www.atoc.org/clientfiles/File/Maps.pdf page 107
Sadly, my interpretation is the Doncaster is not a permitted route for South Elmsall-Scarborough.
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He meant York-Leeds, but there is at 2303 but I think it's irrelevant.
Good spot, used to be routed via Doncaster. Clearly its booked an HST now then. Point rescinded.