Arriva Herts & Essex route 331 Hertford - Royston. A good ride through some of the more rural parts of Hertfordshire and linking the pleasant market towns of Hertford and Royston. 7-8 journeys per day. An end to end journey is about 1hr 20mins. See http://www.arrivabus.co.uk/default.aspx

You can get to Hertford by Arriva (Greenline) 724 from Heathrow Airport, Watford and Harlow amongst other places - or by 310 from Waltham Cross. From Royston you could continue by Stagecoach 26 to Cambridge.