Experts have uncovered the remains of an Iron Age roundhouse, suggesting the site has been occupied since about 100BC, the time of Julius Caesar's birth.
It is believed the area was developed in Roman times with a series of ditches and pottery dating back to the second and third centuries.
High-status Samian pottery imported from Gaul, some of which still bears the potter's stamp, was also found by the Oxford Archaeology team.
Also among the finds were 40 oyster shells, which experts believe show signs of a ritualistic offering.
The site housed a nursery until 2004 when the Unwin family sold the business to Westland but retained the land to sell to developers.
The planned redevelopment of the site will see the building of 35 houses.
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