It is the Nissan Qashqai at an average price of £11,743, at an average age of 37 months old and selling in an average of 15 days, the company's data shows.
Rupert Pontin, Glass's Head of Valuations, said: "The Qashqai has developed a firm following in recent years and is now recognised as offering excellent value for money. When the whole package is considered the comfort and economy amongst other things tick boxes for private and business buyers."
The result for London gave a fascinating insight when compared to the priorities of different buyers in different parts of the country, he added.
"The Qashqai has a lot of appeal because it combines offroad style with family-friendliness. It is interesting to contrast this with the fun and funky Fiat 500 that tops the list in Birmingham and the mainstream practicality and value of the Skoda Octavia, the bestseller in Manchester."
Nationally, the overall bestseller is the Dacia Sandero Stepway, taking 27 days to sell at a price of £8,346 and an average of 12 months old.