The story
Modelled on the Milford Proving Ground operated by General Motors (GM) in Michigan, construction began in 1968. It was created by GM's UK subsidiary Bedford before control was transferred to GM's Vauxhall brand. A first class proving ground requires both hills and flat land, so the traditional choice of a former Royal Air Force airfield, used by many other automotive companies, was ruled out. Many sites around the UK were surveyed before Millbrook chosen. It had the additional benefit of being close to Vauxhall's production site at Luton.
Construction began in 1968, and once it opened in 1970 it became the test site for many European GM subsidiaries including Vauxhall and Bedford.
When Bedford withdrew from the bus and truck markets in December 1986, GM put Millbrook up for sale. In 1988, the site was transferred to a new company, Millbrook Proving Ground Limited as part of Lotus and it offered its facilities to non-GM companies. When GM sold Lotus in 1993, Millbrook was transferred to GM Holdings UK Limited, as an independently managed company which diversified into all aspects of vehicle testing including emission control. In October 2013, it was purchased by Rutland Partners. In September 2016 it was sold to Spectris. In December 2020 it was announced that Millbrook would be divested from the Spectris portfolio of companies and acquired by UTAC CERAM for £133 million. The sale was completed on 2 February 2021.
From Wikipedia’s article on Millbrook Proving Ground, shared under CC BY-SA 4.0.4