The furthest back that anyone is known to have traced unbroken ancestors is Robert Thrale who died in 1538 in Sandridgebury, Hertfordshire. Robert is said to be buried "the medle Aley" of St. Leonard's Church [3] in Sandridge.
Links
[1] http://www.thrale.com/user/login?destination=comment/reply/321%23comment-form
[2] http://www.thrale.com/user/register?destination=comment/reply/321%23comment-form
[3] http://www.thrale.com/thrales_sandridge