The open days take place in July for Oxford and Cambridge. If you can’t make these, there is another chance in September.
It is always best to book in advance because they are very popular. Just go on to the open day websites of Cambridge and Oxford for details.
As well as open days, there are opportunities to shadow students at Cambridge and and and to attend masterclasses and study days. Look on the websites for details about when and how to apply.
And don’t forget the UNIQ and Sutton Trust summer schools are great ways of finding out more about everything related to Oxbridge.