Welcome to POTTERS BAR in north Middlesex
The Middlesex Urban District of Potters Bar was incorporated in 1974 into the Borough of Hertsmere along with Hertfordshire’s Urban District of Bushey, Elstree Rural District and Aldenham Parish.
Elstree Village, now in the same local authority as Potters Bar, is half in Middlesex and half in Herts. The Middlesex half is split between the parishes of Whitchurch aka Little Stanmore and Edgware, with the south-east quarter in the latter and the south-west in the former.
Other links that will be of use to you:
Middlesex – British History Online
GENUKI – Genealogy – Middlesex
The Association of British Counties