The Oxford and Cambridge rowers race each year on the Thames in the Varsity Boat Race from Putney up river to Mortlake. Their crews just over a quarter of an hour to row the 4.2-mile (6.8 km) course: Cambridge hold the course record since 1998 (16 min 19 sec; average speed 24.9 kilometres per hour - 15.5 mph).
We just walked the opposite direction, finishing in a riverside pub in Putney for GOC London's Christmas lunch. The Thames meanders here as it passes under Kew Bridge, Chiswick Bridge, Barnes Bridge, Hammersmith Bridge and Putney Bridge: it's more direct to not follow the river but that wasn't the point. The path along the south bank is maintained but not paved for most of this route and was a little muddy from recent rain; there are birds and trees but much of the interest is in the architecture and the various bridges. The path becomes concrete or tarmac at the boat houses at Putney Reach and stays hardened all the way past numerous blocks of flats until much further down stream. NB faces blurred intentionally.