Because there were so many houses for the government to rebuild, and only so much money, materials and manpower available, they often roughly cleared bomb sites and erected cheap, temporary dwellings called prefabs. The owner was then given a certificate they present later on to demand a proper house be built instead.

However, for some reason many people became so attached to their makeshift houses that they continued living in them for decades, with an incredible number of them surviving into the 90s, only to be finally knocked down and replaced by brick houses when the original owners started dying off and property developers bought up all the land.

Because bombs were dropped in 'sticks', you'd often get a stretch of a terraced road that was levelled, with prefabs put up in their places. This meant developers were very keen to buy the whole row so they could replace all the plots with a single block of flats rather than new houses, making more money. Most original owners refused all offers and pressures (some developers used dirty tricks to try to drive them out, failing to consider they were dealing with a war generation who had taken on the Nazis), remaining in their prefabs even when tall houses and flats went up all around them. As I say, that's why they used to be a very common sight in former target areas like London until the 90s.

It's amazing to think in an age where people don't hesitate to sue someone because they fell over in the snow, that it used to be very common to lose your house and not bother claiming a new one!

As far as I know, the certificates never expired, so I wonder what would happen today if a 90 year old living in a prefab tried to cash it in?

You can search for photos of prefabs on Google Images and Flickr etc.