Graeme Wall wrote:

Doubtless there will be a few more as the Olympic works continue. Some years
ago I was told by a bomb-disposal expert that something like 30% of the
munitions dropped and fired in WW2 didn't explode when expected.

There are many thousands of known unexploded bombs throughout the
Country, with hundreds in Greater London.
The location is even detailed in some cases - e.g. 'In backyard of 13
Wester Road'.

See this site for a quick list of known bombs:
http://www.contaminatedland.co.uk/sere-dip/estd-uxb.htm
Other sites go into more details.
Alan
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