Andrew joined Lanyon Bowdler in 1989 after having worked for several years in Greater London. He gained his law degree from Exeter University and passed his Solicitors' Final Examination at Chester College of Law. He is a registered Trusts and Estates Practitioner and also a member of the Law Society and Solicitors for the Elderly.

His specialist knowledge is in the administration of deceased's estates and affairs of persons under a disability. Andrew also specialises in the preparation and administration of trusts, wills and powers of attorney, Inheritance Tax planning, Court of Protection Receivership cases (particularly those involving head injured clients) and taxation issues regarding the above. He enjoys assisting the elderly in the management of their affairs and has dealt with several cases which involved handling estates in excess of £1 million.

Andrew is recommended in the 2010 edition of the Legal 500, which comments "Andrew Oxenham offers up appropriate solutions".