Kyle Lafferty’s double helped to ease Hearts into the last eight of the William Hill Scottish Cup as they recorded a comfortable 3-0 Tynecastle win over St Johnstone.

A tight hamstring meant Craig Levein’s team were without Steven Naismith as they took on Tommy Wright’s side for the second time in a week.

But the Scotland forward was barely missed as the Jambos took control early with Lafferty’s opening strike, which was then followed by a stunning second from on-loan Manchester United defender Demetri Mitchell nine minutes after the break.

And Hearts’ place in Sunday’s quarter-final draw was sealed when Lafferty struck again soon after to extend Saints’ run of woe to one win in their last seven games.

They found themselves behind after just seven minutes and it was entirely self-inflicted.

Joe Shaughnessy aimed a throw-in at Murray Davidson in the centre-circle but the square angle allowed Arnaud Djoum time to sneak in and intercept. The Cameroonian quickly fed the ball through to Lafferty, who punished Shaunghnessy’s carelessness by angling a left-foot finish past Alan Mannus.

Davidson’s attempt to make amends for his part in the set-back saw him rob Joaquim Adao as the new Jambos recruit dawdled on a pass from Aaron Hughes.

The on-loan Sion midfielder had to pull back his Saints rival as he bared down on Hughes but there was no instant leveller as David Wotherspoon tugged his free-kick attempt just wide.

As the game ticked towards the half-hour mark and with Saints no closer to levelling, Wright decided to shake things up, throwing on a second striker in Denny Johnstone, to the obvious disgruntlement of the man he replaced – Chris Millar.

But it made no difference as Hearts continued to dominate. Ross Callachan came close to doubling the hosts’ advantage moments into the second period as he swivelled onto Lafferty’s knock-down before flashing wide.

But there was no let-off for Saints in the 54th minute as Mitchell’s sensational strike killed off the 2014 winners’ Hampden dreams.

Youngster Anthony McDonald released Djoum down the right, who did well to spot Mitchell’s run inside from the opposite wing.

The Old Trafford trainee still had it all to do but made it look effortless as he arrowed an unstoppable drive into the postage-stamp corner.

And the Gorgie faithful were celebrating again just four minutes later as Lafferty found Michael Smith out wide before darting onto his return pass to slot home number three.

McDonald nearly rubbed salt into Saints’ wounds late on but Steven Anderson prevented the fourth by clearing off the line.