For a long time a battle has been carried on between those who say that it is improper to use mutual in the sense of "pertaining to both parties", "common", as in the phrase "Our mutual friend", and those who, like Dickens, insist on so using it. The Oxford English Dictionary says that this usage goes back to the sixteenth century, but that "it is now regarded as incorrect". Possibly the reason why it persists so stubbornly is the ambiguity of "common". "They have common ancestors" may be misunderstood. While the battle is undecided the prudent writer will confine his use of mutual to the universally accepted meaning of reciprocal (as in "mutual admiration society") and will so avoid the risk of giving offence or being thought ignorant.