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
Foggy and misty overnight with temperatures below freezing
Missed out on Monday's 'Wales This Week, Dylan's Legacy'? Catch up here:
The two projects going head-to-head today are: For the Young at Heart and Y Gwndwn.