What is the duty of care owed by the owner of a premises to a person who comes onto those premises as an invitee?

The classical and universally accepted statement concerning the duty of care owed by the owner of premises to a person who comes onto those premises as an invitee is contained in the judgment of Willes, J. in Indermaur v. Dames [1866] L.R. 1 C.P. 274 at page 288: "And, with respect to such a visitor, at least, we consider it settled law, that he, using reasonable care on his part for his own safety, is entitled to expect that the occupier shall on his part use reasonable care to prevent damage from unusual danger, which he knows or ought to know, and that, where there is evidence of neglect, the question whether such reasonable care has been taken by notice, lighting, guarding or otherwise, and whether there was contributory negligence in the sufferer, must be determined by a jury as matter of fact."