For no particular reason, over the past 2 months I've been upping mileage to 8-12 miles a run. Surprisingly, even in central London that's achievable in pleasant, traffic-free surroundings.
The Serpentine Running Club has some excellent suggestions.
Yesterday I did The Three Parks (9 miles door to door):
Flat route through the Royal Parks - Hyde Park, Kensington Gardens, Green ParkThe Royal Parks are enormous English gardens at their very best, and their Spring magnificence compensated for the need to dodge toddlers, tourists, and rogue cyclists.
and St James's Park - passing historic buildings such as Buckingham Palace, Big
Ben and 10 Downing Street.
Today combined two runs - Regents Park & Primrose Hill plus part of Hampstead Heath (11 miles). The latter included the challenging Parliament Hill, from the top of which you see all London from the Houses of Parliament to the City - the view gives you an excuse to stop. London's enormous horse chestnut trees are in full flower and divert the mind's eye from aching muscles.
Magical (that's the endorphins speaking).