Halfpenny kicked another nerveless three points, after the Lions earned a further penalty at the scrum.
When the Australian forwards couldn't live with the Lions at scrum time yet again, prop Ben Alexander was sent to the sin bin.
Halfpenny again made no mistake, to extend the Lions' lead to 19-3 after 26 minutes.
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Cloud will become more widespread this afternoon but expected to stay dry. Overnight, winds likely to strengthen with rain at times