North of the Thames, people seem to think of South London as one great undifferentiated blot of unpleasantness (with exceptions made for Greenwich and Dulwich, while Blackheath Village always was a minor southern outpost of Hampstead).
Anyone who lives, or has ever lived in a postcode beginning with 'S' will know how wrong this view is.
The east-west divide on the sunny side of the Thames is just as strong as the rivalries that can flare up between the benighted denizens of the W, NW, N and E zones.
And although there is no simple "S" postcode, there certainly is a central south London zone that has no interest in knowing what goers on either side of it. Central South London stretches from London Bridge to Vauxhall Bridge, and takes in Borough, Bermondsey, the Elephant, Kennington, Vauxhalll and Stockwell, the zone tapering out in final southern glory at Brixton Hill.
Although Brixtons's codes are SW, it is just as much south London heartland as Lambeth Walk and Bermondsey Street.
Sticking strictly to inner London - roughly the same as zone 2 on the TfL map - you'd have no trouble naming the adjoining South West and South East neighbourhoods.
SW - which of course shares a postcode prefix with some very posh neighbourhoods across the river - is simply Clapham, Battersea, Wandsworth, Balham, Putney. All of which suffer from their image as being the not-quite-so-rich-bastards' alternatives to Fulham and Chelsea.
Similarly, for SE we have Camberwell, New Cross, Peckham, Deptford, Brockley and Lewisham. But these prickly places have no such shame, they do not need any reflected glory from north of the river.
So, what about all those other places? Tooting? That's the beginning of outer south London, having more in common with Mitcham and Norbury.
Blackheath and Greenwich? They are both distinctly different, they're not in the same game at all.
Blackheath, as already mentioned, is simply oh too nice to really be in the same borough as Lewisham, Eltham or Catford. Greenwich is a weird mix of historic royal Park, posh village (Crooms Hill etc) and former naval base which also retains a hint of the scruffy Kentish estuarine resort.
Similarly out to the west, Richmond and Twickenham have more in common with the plump Thames Valley towns of Marlow or Henley than anything in London. Barnes, too, is truly Surrey-by-the-river.
So let's get back to the core SE and SW areas. What's the big difference?
The first, clinching factor is landscape. South East London is built on a Roman pattern of hills - seven of them - which lap like great waves towards the city. Rising above Brixton and its own hill, we have Tulse Hill, Herne Hill, Denmark Hill, Champions Hill, Knights Hill. Moving East gain, Telegraph Hill, then further south, Sydenham Hill, Gispy Hill, Forest Hill.
Overlooking Greenwich - providing the best view of London anywhere - we have the park and Shooters Hill. On the southern horizon, the hills of Crystal Palace with their twin TV towers.
SW, by contrast, is unudulating plateau falling into marshland. Clapham, Wandsworth and WImbledon commons are relatively flat. Lavender Hill is a gentle bump in the road. Putney has a hill, but it's mostly tarmac and the view from the top is just not up to the amazing views you get in south east London. WImbledon has some mild hills but they tend to be associated with tennis players.
The topogrpahy means that SE London's parks are all far more interesting: contrast Greenwich Park, Brockwell Park, or Dulwich woods with the dull commons of SW4 and SW11. OK RIchmond PArk is beautiful but that's too far out to count.
The second big difference is public transport. SW has tube lines, SE does not. But SE now has the DLR as far as Lewisham and London Overground/East London line linking it with the great orbital movement of rail's version of the M25.
It's clear to me SW's tube lines are actually the bane of its life - that hideous tract of the Northern Line from Kennington down to Mordern is what attracted all the city workers to the area.
The next difference - wealth. Traditionally SW was richer, maybe because most of the money in Kensington and Chelsea tended to leach across the river to the nearest adjacent boroughs and then out down the A3 into the stockbroker belt.
But this is to oversimplify. Look at the architecture: by far the finest suburban villas of the 19th century were in SE postcodes. There's no better street of grand domestic architecture in all of London than Camberwell Grove. The beautiful houses surrounding Blackheath and Greenwich parks are more elegant than any of that brash stuff in NW3.
Those were the days when the most successful actors and writers headed for the wooded slopes of south east London to escape the stinking wen.
The miserable clerk, meanwhile, were shunted towards the endless Victorian terraces of Clapham and Battersea. Comforting as these now seem, they are pinched in comparison, and cynically repetitive.
Arts and entertainments is the next category, and again SE sweeps the board. Each of the centres - even including New Cross and Peckham - has internationally famous music and art venues, there's Horniman's Museum and the Dulwich art gallery, Depford's Laban Dance centre, Goldsmith's, and the joys of Camberwell.
Overall, you have to admit that SE London is the victor here: it always had the edge, to be honest.
After those vital three decades in the darkness, it has again been rising and shows no signs of falling away. Peckham the new Dalston, etc.
Whereas SW is stale, saturated, and over-populated with the sort of recently-young couples with small kids who make you want to stay well away from all pubs on any day there's a big "rugger" game, and well away from all public spaces when the sun shines. Sorry, Clapham, but you blew it all away in about 1980 with the arrival of Foxtons and their yuppie clientele.
My advice - do the estate agent's old trick. Ditch the name, Clapham, replace it with "West Brixton".
Oh, and the last word on all this: the word is Death. We all die and need somewhere for our bodies or ashes to rest. SE London has two of London's "magnificent seven" Victorian cemeteries - Nunhead and West Norwood. SW has none.