It was done the moment the 99 year lease ran out and the UK handed it back , the Chinese would not tolerate a visible relic of the Opium wars being dictated to by foreigners i.e 2047 Basic Law guarantee.
They tore up the agreement when it became expedient (they declared "historical document of no significance") to do so.
They tore up the agreement when it became expedient (they declared "historical document of no significance") to do so.