1950s/1960s development in London

[mallguy]

I love London, and I think it's a beautiful city. Nonetheless, there is a decent amount of 1950s/1960s modernist architecture there that I assume was built to replace WWII destruction. Thus two questions:

1. About how much of London was destroyed due to WWII- is 15% about right?

2. In the 1950s and 1960s, was there a development wave that led to the redevelopment parts of pre-WWII London that were still there?

Basically, are the 1950s/1960s buildings there mainly because of WWII, or would they have happened anyway?

Thanks.