 Complete the following phrase:  In 1974 the Department of the Environment purchased the estate with the intention of giving it to the London Borough of Barnet in exchange for open land at Henlys Corner intended for a flyover, which was never built. The farm was leased by Chris and Jane Ower, who ran it as a popular local attraction from 1980 until February 2001, when the site had to be closed because of restrictions caused by the 