Benfica took the lead in slightly fortuitous circumstances as Franco Cervi saw a well-struck effort bobble into the net courtesy of a couple of deflections off Per Mertesacker.
Arsenal responded well to that setback with Walcott scoring a quickfire double thanks to a couple of precise finishes from close range before Eduardo Salvio capitalised on some dreadful defending to equalise on the stroke of half-time.
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However, the hosts cruised to victory in the second half with a Lisandro Lopez own goal and further strikes from Olivier Giroud and Alex Iwobi handing them a comfortable win in front of an expectant home support.
More to follow…