The man arrested this morning is the sixth suspect to be arrested - and the seventh person to be questioned - in connection with the Yewtree operation which involves a team of 30 officers and has already cost around £2 million.
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Authorities have warned that the death toll is likely to rise as much of the building is yet to be searched.
The PM will sound out the possibility of new free trade agreements with Gulf states for once the UK has left the EU.
In the unexpected announcement on Monday, Mr Key said it was the "right time" to leave politics.