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.
More top news
There'll be bracing winds and heavy showers this afternoon and expect a wet and windy start on Monday morning.
Carl Edwards and guests look back at the week's events in the latest edition of Newsweek Wales.
A Yellow Warning has been issued by the Met Office as gale force winds and showery rain affect areas across Wales.