Here's a statement by Oxford uni on their Chancellor from when they had their elections in 2003.
Statement by Council on the characteristics of a Chancellor
For the guidance of candidates and electors, Council has agreed to publish the following statement about the Chancellorship.
The Chancellorship is not an executive office and the formal duties are relatively few. Chief amongst these are presiding at ceremonies such as Encaenia and at the Chancellor's Court of Benefactors and also, if the Chancellor wishes, chairing the Committee for the Nomination of the Vice-Chancellor. The office is, however, much more than symbolic (important though its symbolic role is).
The Chancellor must be visibly committed to the independence of universities and to the values for which they stand. He or she must have the stature, both intellectually and in all other respects, appropriate to Oxford's position as a leading international university and, through his or her own qualities, must be able to enhance the University's reputation both within the UK and abroad. He or she must have the confidence and ability to preside convincingly at occasions such as Encaenia and to take the leading role as far as possible at the many other official events which the Chancellor is likely to be called on to attend in the University and its colleges, and from time to time as the University's representative at major occasions outside Oxford. The Chancellor is ex officio Visitor of five colleges and the person appointed must also be appropriate for this role.
The Chancellor must have wide experience which can be drawn on when required to support and further the purposes of the University. He or she must be a person of integrity and have tact, discretion and sound judgement, being able to give advice and guidance when called on, particularly by the Vice- Chancellor. He or she must be sensitive to the University's aspirations and to the concerns of current students and staff, and an authoritative figure capable of presenting the University's interests to a wide variety of constituencies, such as major world figures, benefactors or potential benefactors, and alumni. For the proper fulfilment of the office, the Chancellor must be readily accessible and available throughout the year to exercise his or her duties, both formal and informal.
Although by tradition the Chancellor has been an eminent figure from politics, law or the church, these are not necessarily the only backgrounds from which a Chancellor might come. The characteristics of those who have achieved distinction in such fields are, however, typical of the characteristics required in a Chancellor and described above.
http://www.ox.ac.uk/gazette/2002-3/supps/1_4645.htm