Other parts of London suffered much worse, however. Not only were there two flood warnings but 14 other flood alerts were issued, supposedly covering most of the capital. But such detail as the BBC reported suggests that the worst affected areas were in either SW London or out to the east, around Walthamstow; see https://www.bbc.co.uk/news/uk-england-london-57963856.
Parts of London's old sewer system evidently can't cope but I suspect that those which can benefit from much better local surface drainage, so that less rainwater floods into the sewers.
Some of the worst-affected areas are hotspots for massive redevelopment of old houses, where vast basements have been excavated and tanked to make them waterproof. All that excluded groundwater has to go somewhere, after all. Flood risk should be a serious consideration when planners assess such selfish planning applications.