You are looking for a small camouflaged round lock-n-lock container.
... to get to the next cache in the series, turn left and follow the route of the Hertfordshire Way through the field, doing your best pirate impression as you go (peg leg optional).
The Hertfordshire Way is a 194 mile circular route on public rights of way around the county that it shares its name with. The course of its journey has been chosen to pass through a variety of scenery, mostly in open countryside but also travelling through some of the more interesting and attractive villages. Hertford and St Albans, as the County Town and main historic centre respectively, are the only large towns on the route which is broken up into a number of sections. Your walk takes you along leg 8 which runs from Kings Langley to Shenley and is way-marked by circular plates displaying the distinctive imagery of the Stag as can be seen here.