Calero, 23, has been tipped to join the Gunners in January, says The Sun.
And last night he shared a snap of himself in the capital, staying at the H10 Waterloo hotel on Southbank.
Centre-back Calero played in Saturday's 1-1 draw with Athletic Bilbao and hopped on a plane to England shortly after.
Earlier this month, the Gunners were linked with the young defender, as they currently sit in the midst of a defensive crisis.
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