Great Trees of London was a list created by Trees for Cities after the Great Storm of 1987, when the general public were asked to suggest suitable trees. 41 were chosen, with a further 20 added in 2008. Time Out published a book 'The Great Trees of London' listing all 61 trees in 2010. Wikipedia has the list.
The Telegraph reported in 2019 that 6 of these trees have since been lost leaving 54 (maybe they have a different version of arithmetic - we make that 55).
The Hardy Ash and the Cheapside Plane are also Great Trees.
Whilst thinking about trees we should mention this London tree map.