Question: Watton-at-Stone railway station runs to the town in which English county?

Context paragraphs:
K339/340 Beijing-Jiamusi Through Train: The K339/340 Beijing-Jiamusi Through Train (Chinese:K339/340次北京到佳木斯快速列车) is a railway running from Beijing to Jiamusi.  It carries express passenger trains for the Harbin Railway Bureau.  The Jiamusi passenger segment is responsible for passenger transport.  Jiamusi originates on the Beijing train.  25G Type Passenger trains run along the Jingqin Railway, Shenshan Railway, Hada Railway, Binbei Railway and Suijia Railway across Heilongjiang, Jilin, Liaoning, Hebei, Tianjin, Beijing and other areas.  The route covers 1675 km.  Beijing Railway Station to Jiamusi Railway Station runs 23 hours and 27 minutes.  Jiamusi Railway Station to Beijing Railway Station runs 24 hours and 18 minutes.

The Finishing Line: The Finishing Line is a short film produced in 1977 by British Transport Films, warning about the dangers children face on railway lines.  Although it is not strictly a public information film, it is often considered to be so by fans of the genre.  It was broadcast in its entirety several times on television, but was so controversial that it was replaced less than two years later by the slightly less graphic "Robbie".  It won at least two creative awards: Certificate of Appreciation (Top Category) and Oberhausen Mention at the Festival of Youth Paris.  The film was also shown in several schools by invitation.  The film was directed by John Krish, written by Krish and Michael Gilmour, and produced by James Ritchie.  It was filmed in the vicinity of the then-closed Watton-at-Stone railway station, Hertfordshire.  The bridge that the boy at the beginning / end of the film is sitting on is the southern side of the Station Rd railway bridge.  The main filming area for the actors was located immediately southwest of the bridge sandwiched between Church Lane and the railway line.  The "stone throwing" 'competition' was filmed immediately north of the railway bridge on the western side embankment where the AWS signal ramp is.  The "Great Tunnel Walk" scene was filmed about 3.5 Miles (5.63 km) south of the current Watton-at-Stone railway station.  The 'start' was at the northern portal and 'finish' was at the southern one.

Watton-at-Stone railway station: Watton-at-Stone railway station serves the village of Watton-at-Stone in Hertfordshire, England.  It is on the Hertford Loop branch line between Hertford North and Stevenage and is served by trains operated by Great Northern.

Alton railway station: Alton railway station is a railway station in the town of Alton, in the English county of Hampshire.  The station is the terminus for two railway lines; the "Alton Line" which runs to Brookwood and onto London Waterloo and the "Mid Hants Watercress Railway", which runs to Alresford.  The latter once ran through to Winchester but was closed to passengers in February 1973.  It reopened as a heritage line in 1985.  Two other routes (both now closed) also served the station – the Meon Valley line to Fareham and the Basingstoke and Alton Light Railway.

Corfe Castle railway station: Corfe Castle railway station is a railway station located in the village of Corfe Castle, in the English county of Dorset.  Originally an intermediate station on the London and South Western Railway (L&SWR) branch line from Wareham to Swanage, the line and station were closed by British Rail in 1972.  It has since reopened as a station on the Swanage Railway, a heritage railway that currently runs from Norden station just north of Corfe Castle to Swanage station.

Swanage railway station: Swanage railway station is a railway station located in Swanage, on the Isle of Purbeck in the English county of Dorset.  Originally the terminus of a London and South Western Railway (L&SWR) branch line from Wareham, the line and station were closed by British Rail in 1972.  It has since reopened as a station on the Swanage Railway, a heritage railway that currently runs from Norden station just north of Corfe Castle to Swanage station.  It now also runs to Wareham on certain services, but not on regular services due to signalling problems.

Stevenage railway station: Stevenage railway station serves the town of Stevenage in Hertfordshire, England.  The station is 27 mi north of London King's Cross on the East Coast Main Line.  Stevenage is managed and served by Great Northern.  It is also served by Hull Trains and Virgin Trains East Coast.

2167/2168 Changchun-Mudanjiang Through Train: The 2167/2168 Changchun-Mudanjiang Through Train (Chinese:2167/2168次长春到牡丹江普通快速列车) is a passenger train running from Changchun to Mudanjiang.  It carries express passenger trains for the Shenyang Railway Bureau, the Changchun segment is responsible for passenger transport.  Changchun originates on the Mudanjiang train.  25B type passenger trains run along the Changtu Railway and Tujia Railway across Heilongjiang, Jilin and other areas.  The 777 km Changchun Railway Station to Mudanjiang Railway Station route runs 15 hours and 23 minutes.  From Mudanjiang Railway Station to Changchun Railway Station runs 14 hours and 54 minutes.

North Elmham railway station: North Elmham railway station is a railway station in the village of North Elmham in the English county of Norfolk.  The station is part of a line being restored by the Mid-Norfolk Railway from Dereham to County School railway station.

D73/74 Beijing-Jilin Through Train: The D73/74 Beijing-Jilin Through Train (Chinese:D73/74次北京到吉林动车组列车) is a railway running between Beijing and Jilin City.  It carries express passenger trains for the Shenyang Railway Bureau.  The Jilin passenger segment is responsible for passenger transport.  CRH5 Type Passenger trains run along the Jingha Railway, Harbin–Dalian High-Speed Railway and Changchun–Jilin Intercity Railway across Jilin, Liaoning, Hebei, Tianjin, Beijing and other areas.  The route spans 1248 km.  Beijing Railway Station to Jilin Railway Station requires 7 hours and 5 minutes.  Jilin Railway Station to Beijing Railway Station runs 7 hours and 21 minutes.

Supporting paragraphs: Watton-at-Stone railway station Stevenage railway station
Answer: Hertfordshire