There have been pickets on campuses as university staff begin a strike in more than 50 universities, in a dispute over pensions.
Lecturers have walked out at universities including Oxford and Cambridge at the beginning of a month-long strike campaign.
Petitions signed by 80,000 students, many backing the lecturers, are demanding refunds for lost teaching.
Universities minister Sam Gyimah has called for more negotiations.
But Mr Gyimah says students "deserve to receive the education that they are paying for. For many, this is a vital…