Hearts manager Craig Levein was naturally delighted to see his side reach the quarter-finals of the Scottish Cup for the first time in six years, and heaved a sigh of relief that his players avoided injury in a typically bruising contest against St Johnstone.

A Kyle Lafferty brace either side of what Levein described as a "beautiful" top-corner strike from Demi Mitchell saw the hosts earn a successive victory over Saints following last weekend’s narrow Premiership win.

Hearts were cruising to victory from the moment Lafferty added his second with a well-worked 58th-minute goal but there was still anxious moments for Levein, particularly when Murray Davidson and Chris Kane collected cautions for clattering into Ross Callachan and Christophe Berra respectively.

“I thought the one on Berra was naughty and it was late,” said Levein. "They had about four or five of those. Years ago we succumbed to that type of bullying. Maybe that's a bit strong a word but teams being physical and seeing if we're mentally prepared to battle to win a match. But we're a different team now. We're not soft.”

St Johnstone actually made the brighter start but contrived to take a wrecking ball to those foundations by making life easy for Hearts to break the deadlock through Lafferty. On loan Manchester United wing-back Mitchell found the top corner with an exquisite strike from outside the area in the 54th before Lafferty added his second.

“Kyle’s first goal was a fantastic finish,” said Levein, who admitted that he left out Steven Naismith due to a minor hamstring injury. “Arnaud [Djoum] stole the ball, played Kyle through and it was a ridiculously tight angle on his left side. Then he gets his second and I left him on hoping he might get a third.

“Demi had been unlucky not to score for us. I was right behind his, that was beautiful to watch. As soon as it left his foot, it was going in the top corner. The biggest thing for me is the delight on his face when he scored.

“Football is a great game when you see kids doing something like that and feeling good about themselves. It made me smile.”

Saints captain Joe Shaughnessy was at fault in playing an ill-advised long-throw into the centre circle for the opener. Djoum read the defender’s intentions and intercepted before Davidson could react and fed Lafferty, who, from an acute angle, still managed to squeeze a left-footed shot past Alan Mannus.

Mitchell then notched his sublime strike. Djoum found the on wing-back after tearing forward on the counter and Mitchell arched a superb effort into the top corner from 20 yards.

The victory was all but sealed four minutes later when Lafferty made and finished the third. Lafferty exchanged passes with Anthony McDonald and then Michael Smith before the towering forward placed a left-footed shot past Mannus from close range.

St Johnstone manager Tommy Wright was furious about the way his side conceded the first goal. “Ultimately when you give away two goals like we did you can’t win a football match,” lamented Wright, who said he feared Stefan Scougall’s season was over with a combination of knee and ankle injuries that forced the midfielder off in the midweek defeat to Motherwell. “I don’t know what Joe is doing at the first, we worked on throw-ins yesterday. And the idea certainly wasn’t to throw it in at Murray Davidson on a bobbly pitch. So we’ve gifted them the first goal.

“We actually started quite well, we caused them problems with Joe’s throws that no one stepped up and attacked.”