One of the oldest universities in the country, UCL has graced the Bloomsbury district of London (adjacent to the British Museum) since opening her doors in 1826. An impressive academic institution this, known primarily for its work in the social sciences and languages. UCL is also home to the formidable Institute of Psychiatry, and her own University hospital, making this an excellent choice for those with a medical inclination.
UCL is also part of the prestigious University of London (alongside places like Kings College and the London School of Economics), giving the degrees they award an extra cachet. The famous University of London Library is situated alongside.
Be warned, UCL is incredibly popular for both home and international students. Competition is intense at all levels, and it is only really worth considering an application if you are a real high-flyer. The excitement of studying in the centre of London could soon wear off after a few weeks of expensive and tiring commuting (accommodation at a reasonable price is likely to be some distance away), so bear that in mind too.
To summarise - one of Londons many world-class institutions.