The National Trust booklet ‘The Cerne Giant & Dorset Hill-Forts’ (2000) which is definately available at the Kingston Lacy house and might be available at other Dorset properties, gives the following directions to the hill fort at Lambert’s Castle, “from Pilsdon continue along the B3164 for 2 km and turn left onto the B3165. Drive a further 3km, the track to Lambert’s Castle is on the left”.
It adds that the name ‘Lambert’s Castle’ comes from the Anglo-Saxon personal name of ‘Lambert’ and that the earliest documented reference to the place name dates from 1044.
Note – the car park is at about SY366988.