The Crossrail archaeology programme has also unearthed its first Bronze Age finds - although these won't form part of the exhibition.
Two wooden stakes, cut by early London hunters with an axe, and a hammer stone have been discovered at excavations at Plumstead.
Historians believe these may have been used to build a large network of timber pathways across east London, which may have made it easier for hunters to catch animals living in the lush wetlands some 3,500 years ago.
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A few members of the team have claimed they are being haunted from beyond the grave.
Boris Johnson's speech was well received by delegates - and was introduced to stage by Zac Goldsmith, the man who wants to replace him.
Showers around this evening and overnight - keeping the temperature fairly mild, but not feeling pleasant.