Oxford was ranked fifth in the world

They are ranked fifth and sixth respectively, after the top American universities in the guide, produced by the Times Higher Education Supplement.

Altogether, UK universities have eight places among the top 50 institutions listed.

The rankings are based on a survey of 1,300 academics in 88 countries, on university research and other factors.

American institutions took seven of the top places, led by Harvard, in first place, the University of California, Berkeley, in second and the Massachusetts Institute of Technology, third.

Europe

London's global significance in higher education was reflected in four placings among the top 50 institutions.

In 11th place was The London School of Economics. Imperial College was 14th, while University College, London was 34th and the School of Oriental and African Studies was 44th.

Apart from the UK, the only other European country featured in the top 20 was the Federal Institute of Technology in Zurich, Switzerland, which was in 10th place.

The highest ranked universities in Asia were Tokyo University in Japan, in 12th position, and China's Beijing University, which was 17th.

Six of Australia's universities were among the top 50, led by the Australian National University in 16th place.

There are other ranking systems.

In September, one published by academics in China placed Cambridge third, behind Harvard and Stanford.