Harwell is a village and civil parish in the Vale of White Horse about 2 miles (3 km) west of Didcot, 6 miles (10 km) east of Wantage and 13 miles (21 km) south of Oxford. The parish measures about 3.5 miles (6 km) north – south, and almost 2 miles (3 km) east – west at its widest point. In 1923 its area was 2,521 acres (1,020 ha). Historically in Berkshire, it has been administered as part of Oxfordshire, England, since the 1974 boundary changes. The parish includes part of Harwell Science and Innovation Campus in the southwest. The 2011 census recorded the parish's population as 2,349.

Didcot is a railway town and civil parish in South Oxfordshire, England, located 15 miles (24 km) south of Oxford, 10 miles (16 km) east of Wantage and 15 miles (24 km) north west of Reading. Historically part of Berkshire, the town is noted for its railway heritage, Didcot station opening as a junction station on the Great Western Main Line in 1844. Today the town is known for the railway museum and power stations, and is the gateway town to the Science Vale: three large science and technology centres in the surrounding villages of Milton, Culham and Harwell.