Five tries — including a brace to Halfpenny, who also enjoyed another golden night with the boot — kept the Lions unbeaten in five games this tour, and gave them their biggest win over the Waratahs in 125 years of visiting Australia.
Halfpenny’s haul was also the highest individual total against the Waratahs — surpassing Jonny Wilkinson’s 19 in 2001 — and was boosted by kicking figures of eight from eight, putting him on 22 out of 23 so far on tour.
But some of the gloss was removed from the big win when a possible hamstring injury forced Welsh centre Jamie Roberts from the field in the final 10 minutes, raising questions about his fitness for the start of the three-Test series.
The Lions, who have been looking for hard matches in Australia, got what they were looking for against the Waratahs, who gave a good account of themselves despite playing without 11 of their internationals.
But the tourists got on with the job and after leading 23-10 at half-time, they scored 24 points in the second half with Jonathan Davies, Tom Croft and Halfpenny all outstanding.
“A tough match for us and we’re very pleased with the outcome and even at the end there when we were down to 14 men (with Roberts injured) we controlled the game without being under too much pressure,” head coach Warren Gatland said.
“In fairness to the Waratahs they took it to us. I thought the guys responded magnificently. I thought the discipline was excellent, so I’m very pleased.”
Gatland was impressed with his team’s discipline with some provocation off the ball, particularly to the halves, Jonny Sexton and Mike Phillips.
“The big key in this game was keeping our discipline and it would have been easy for someone taken late to lose their head and throw a punch, and that being picked up and leading to a citing,” Gatland said.
“So from that point of view I think our discipline was absolutely fantastic.”
Gatland also paid tribute to centre Davies, who had an outstanding match.
“I thought he was fantastic. Given the quality of our midfield and the pressure he was under to respond and that I thought it was one of the best games I have seen him play,” he said.
Irish winger Simon Zebo, who only arrived this week as injury cover, was over the try-line with his first touch of the ball in the opening minute but his foot clipped the touchline and the video referee ruled no try.
But the tourists crossed again for their first try in the sixth minute when Davies put flyhalf Sexton over with a beautiful inside pass for a 10-0 lead.
The feisty Waratahs hit back when winger Peter Betham swept on to Bernard Foley’s crossfield kick and passed inside to centre Tom Carter, who scored in the left corner.
However, Halfpenny was deadly accurate with his goal-kicking and two penalties gave the tourists a 16-7 lead after 27 minutes.
The Waratahs had their best period of the half as they ripped into the Lions with ferocious tackles and edged to within six points with a Brendan McKibbin penalty.
But the Lions finished the half strongly with Halfpenny crossing wide out on an overlap, after the Lions’ forwards had taken play to within metres of the home side’s try-line. Halfpenny’s conversion gave them a 23-10 halftime lead.
After the break, the Lions picked up where they left off and Halfpenny scored his second try off a clever short pass from Davies to scoot over, and then added the conversion.
But the Waratahs quickly hit back when impressive big lock Will Skelton won the ball in a maul and found Carter for the centre’s second try of the match.
England flyhalf Owen Farrell came on for Sexton in the 49th minute as the Lions led 30-17.
Halfpenny kicked another penalty before Davies was quick off the defensive line and intercepted the ball, leading up to blindside flanker Croft storming over for his team’s third try and a 40-17 lead.
Coach Gatland used the opportunity to bring all his remaining seven replacements off the bench and rest his potential Test stars for next week.
Davies capped a great match when he scored his team’s fifth try with eight minutes left.