The building is a large corner block, built in Victorian times next to The Oval Cricket Ground, (to hide the gasworks behind), hence its name. It had 8 entrances and staircases, in other words there were really eight houses built in a group. Mansions in London contain flats, so from each of these staircases 6-8 flats were accessible.
Used to be owned and forgotten by Lambeth Council, in the 80-s was taken over by squatters, evicted in 2000. They were amongst the most desirable squats in town, having a perfect view of the cricket ground.

The building complex was sold and totally refurbished, now luxury flats. When available, a flat costs over half a million pounds to buy (the "season ticket" to the cricket matches trown in). :-)

It is not a "community" as such, and not a particularly large block by London standard, not even a typical mansion block, because they are nearly always built of red brick.

There are no communal facilities, except two communal roof terraces.

At the time of the sale for refurbishment:
http://web.ukonline.co.uk/localonline/d/0076ovma.htm
http://www.eigroup.co.uk/ImageLib/LotPhotos/and/20030410/42....

Now:
http://r.foxtons.co.uk/1185854384/chpk0112325-ll.pdf

www.findaproperty.com/searchresults.aspx?edid=00&salerent=0...

--------------------------------------------------
Note added at 3 hrs (2007-10-24 19:29:11 GMT)
--------------------------------------------------

Typo: thrown in

--------------------------------------------------
Note added at 3 hrs (2007-10-24 19:35:20 GMT)
--------------------------------------------------

If the person was living there during the squatters time, then of course there was a "squatters' community", they knew each other and they were held together by common interest - to be able to stay there as long as possible.