If your ancestors came from England, you should be able to trace some of your lines back to the mid 1500's. If, however, you can trace an ancestor to a royal line or a noble line, then it may be possible to trace your ancestors considerably further back. The royal line of Britain can be traced back with some certainty to King Cerdic of Wessex who died in 534.
According to medieval authorities, Cedric was the son of Elesa, the son of Elsa, the son of Gewis, the son of Wig, the son of Freawine, the son of Freothgar, the son of Brand, the son of Baldeg, the son of Wodin, the son of Frealaf, the son of Finn, the son of Godwulf, the son of Geat, the son of Tetwa, the son of Beaw, the son of Sceldwa, the son of Heremond, the son of Itermon, the son of Bathra, the son of Hwal, the son of Bedwig, the son of Sceaf who was born in Noah's Ark, the son of Noah.
Chapter 5 of Genesis gives the descent of Noah from Adam through Seth, Enos, Cainan, Mahaleel, Jared, Enoch, Methuselah and Lamech. If you check your bible you'll find it omits to mention that Noah had a son, born in the Ark, called Sceaf but, I suppose that every pedigree has a weak link in it somewhere. Don't believe in Adam and Eve? Well recent research into human DNA indicates we all originated from a far smaller gene pool than the other primates.
Until recently it was thought that we would never be able to trace ancestry back to a single
cell life form, since they did not keep much in the way of records. However, give science a few years! Already scientists have discovered a way of using DNA to trace ancestors where weak links occur. Who knows? In a few years you might find your 240,000,000th cousin is the Beech tree growing in your garden!