" Context—where you find an object—is more important than the actual object. In policing it’s whether the broken glass is on the inside or the outside. In archeology it’s whether that datable coin is found in the wall foundations or its demolition infill. You can live without the coin, but you need the dating information. “Material was taken from about five sites,” said Adrian. “I’ll have to check the reports to be certain, but as I recall it was nearly all Roman brick. "

― Ben Aaronovitch , Lies Sleeping (Rivers of London, #7)