This Royal Observer Corps post opened in 1958 for the detection of nuclear blasts in the event of the Cold War going hot. The small bunker was not manned for very long, closing in 1968. It is believed that the Cold War monitoring post was constructed on the site of a WWII-era post.
It is located within a small compound at the top of Vange Hill in a bushy area amongst Basildon Golf Course. The compound survives relatively well, with an original tall pallisade fence still in situ (although one side of the gate has fallen off). Surfaces features are still extant, although the post shaft itself has been capped with concrete. When Subbrit visited in 1997 before capping, it was in a very poor stripped and burnt-out condition.
The image below, from Basildon Heritage, shows an ROC post with an Orlit observation tower in reference to Vange, although it is not clear if this actually shows the Vange post or is in fact of a different post.
Sources: Subbrit.org.uk, Basildon Heritage