Hadleigh is a town and former civil parish that is within the borough of Castle Point, located in the southeast of the county of Essex, England, on the A13 between Thundersley, Benfleet and Leigh-on-Sea with a population of 18,300.

[2] Based on the previous census, writing in 1848, Samuel Lewis, summarised the facts of its history and economy as follows: In the 19th century, Hadleigh was the home of the cunning man James Murrell.

[6] The castle ruins are set at the top of a hill overlooking the Thames Estuary, and the Canary Wharf development nearly 30 miles to the west can be seen when visibility is adequate.

Existing farm buildings were renovated and new dormitories, a bathhouse, laundry, reading room, hospital and religious meeting house were built.

Employment at the training centre – reminiscent of the colony's origins – includes horticulture, carpentry, catering, office skills and estate management.

[7] As of the 2010 general election, the Member of Parliament representing the parliamentary constituency of Castle Point (created in 1983) is Rebecca Harris of the Conservative Party.

It was announced in August 2008 that Hadleigh Farm (including the area around the castle) would host the London 2012 Olympic mountain biking events.