509. Effect of waivers and licences.

Where any actual waiver1 by a lessor2 or persons deriving title under him of the benefit of any covenant or condition in any lease3 is proved to have taken place in any particular instance, such waiver is not deemed to extend to any instance, or to any breach of covenant or condition save that to which such waiver specially relates, or to operate as a general waiver of the benefit of any such covenant or condition4, unless a contrary intention appears5. Where single breaches of a covenant have been continually waived, the landlord is not debarred from exercising his