tottenham hotspur plan to build a new world-class 56,000-seat stadium .
plan is for new stadium at white hart lane to open for 2018-19 season .
archway sheet metal works , final opponent to move , is being demolished .
part of the premises is being knocked down now and the rest will be done when archway find a new premises .
tottenham 's new stadium is expected to cost around £ 400million to build .
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