The one-and-a-half-acre roof garden was built in 1938 as a glorious appendage to Derry and Toms, then one of London's finest department stores. Although from street level it may beggar belief, the garden contains a stream, ducks and fully grown trees, whose leaves one can glimpse from the pavement below. A pair of male pink flamingos also live here, abandoned by their female companion which flew off a few years ago. The garden incorporates three distinct styles: a formal Spanish arrangement with a court of fountains; a red-brick Tudor layout; and an English garden. All this perches on a mere two and a half inches of soil - water comes from an artesian well 500ft below street level, while a fan-shaped system of drains prevents any leaks through the ceiling into the underwear department of M&S beneath. It is now owned by the Virgin group, who use it as a private club, but is open to the public when not in use, and entrance, via Derry Street, is free (0171-937 7994).
Despite the boldness of its roof, the former Derry and Toms building is unremarkable alongside the 1930s art-deco scheme of Barkers next door, the other great store on Kensington High Street. The current building was constructed between 1929 and 1931, and owes much to Chicago architect CA Wheeler. Barkers' executives of the time admired the planning and design of American stores, and had doubtless been impressed by Selfridges, which was completed in 1928 following the designs of Daniel Burnham, also from Chicago. The building has a vibrancy missing from most of the rest of the street due, in part, to its projecting tower staircases and a continuous canopy at street level which picks up the natural curve of the road.
Kensington Square, in contrast, is the oldest residential square in London. Originally called Kings Square, it was laid out in 1685 by a woodcarver and joiner called Thomas Young, and became highly fashionable when William III bought nearby Nottingham House and converted it into Kensington Palace. Distinguished former residents include John Stuart Mill, who lived at No 18, and the political philosopher Thomas Carlyle. Today, the pretty garden square is still remarkably peaceful given its proximity to the shops and traffic - it has a view of the roof garden, and nearby Thackeray Street is a good stopping-off point for an implausibly priced cup of coffee.
St Mary Abbott's churchyard, on the other side of the high street, is another wonderfully tranquil spot with shaded benches and cool walkways, and can be found along the alley opposite M&S.
So, if trudging along Kensington High Street leaves you feeling short- changed, there are plenty of fascinating alternatives that won't cost you a penny.