Hi I did understand your concern. Anxiety especially at this age and with his competitive environ in oxford would be an arduous task. The best way to tackle anxiety is by talking to loved ones and friends about it and to adopt and learn certain relaxation techniques like deep breathing, counting 1-100 and so on. For long term you can advice him to learn meditation and yoga from a nearby teacher or from internet and try to imbibe it in his life. As far as medications are considered there are certain antianxiety drugs like benzodiazepenes and beta blockers and buspirone, but they are to be taken only under doctors/pschyiatrist guidance only I hope this helps wish you and your son all the best.