The parish of Idmiston contains three villages on the river Bourne and since, the mid 20th century, Porton has been the best known because of the chemical and microbiological research station that has been there since 1916.

The greater part of the airfield of Boscombe Down is in Idmiston parish although the base itself is in Amesbury parish. Boscombe Down opened in 1917 as a flying training unit. After being home to various squadrons the station was taken over by the Aeroplane and Armament Experimental Establishment that had been set up at Martlesham Heath in 1917 after its initial work at Upavon Central Flying School. A & A E E (now operated by QINETIQ) has remained at Boscombe ever since.

For much of the early 20th century most of the parish has been owned by the government to accommodate the airfield and Porton Down.

A War memorial, in remembrance of those men from Idmiston and Porton who died in the two World Wars, in the form of a simple stone cross stands in the churchyard of St Nicholas Church, Porton. A little distance away also stands a Memorial Hall erected in more recent times.