The Prime Minister is hosting a PM Direct event at the factory of a defence contractor in Glasgow.
He opened by praising the "incredible periscope" aboard HMS Victorious - the nuclear submarine he visited earlier - which was manufactured by the firm that is hosting his talk.
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Explosives experts were called to the nuclear reprocessing site in Cumbria, to help deal with chemical substances.
The arrests were made on suspicion of producing and disseminating pedophilia content on the internet, the country's Justice Ministry said.
The A4-sized sketch originally went for £75 when it was first sold.