Ivorian midfielder Mohamed Diomande lit up a dull first half in the 37th minute when he fired in from 25 yards for his first Gers goal since arriving in the winter transfer window.

Tavernier then dispatched penalties after 79 minutes and 87 minutes, both following VAR intervention, taking his tally for the season to 19.

With 12 fixtures remaining, Philippe Clement’s side are two points clear of their Old Firm rivals and will take the momentum of nine straight wins into next week’s game against third-placed Hearts at Ibrox.

Rangers fans travelled in great expectation for the lunchtime kick-off and again they noted that Clement had rung the changes, mostly in attack, with Borna Barisic, Oscar Cortes, Scott Wright, Diomande and Fabio Silva returning.

Craig Levein’s 10th-placed side had Dan Phillips back from injury, with Connor Smith and Ryan McGowan back.

A poor surface was always going to make passing football difficult and the ball spent a lot of time in the air in a scrappy start to the match.

Rangers had 43 attempts on goal in the 3-1 win over Ross County in midweek — 23 on target — but had yet to trouble Saints keeper Dimitar Mitov until Diomande stepped up to break the deadlock.

Another Rangers move looked to have broken down at the edge of the box with McGowan nicking the ball away from Silva.

However, it fell to Diomande and the midfielder, on loan from Danish side Nordsjaelland with the Light Blues having an obligation to buy in the summer and making his first league start, took a touch and drilled it past the diving Mitov.

Dujon Sterling, back from suspension, replaced Gers winger Wright for the start of the second half with Saints striker Benjamin Kimpioka on for David Keltjens, who had been booked in the first half, and the game opened up.

Within seconds of the restart Mitov made a fine save from Silva’s close-range drive from a Diomande cross before Sterling just failed to get enough on a cross from the hard-working Todd Cantwell, who was soon replaced by Tom Lawrence.

Rangers’ narrow lead ensured St Johnstone remained in the game but in the 65th minute Sterling had another chance when he was played in by Silva but took too long to get his shot away and was eventually crowded out.

Three minutes later striker Cyriel Dessers and winger Ross McCausland replaced Silva and Cortes as Clement looked to grab the second goal to give his side some breathing space.

When St Johnstone’s veteran defender Andy Considine fouled Sterling, although he did not point to the spot at first, referee Matt MacDermid was asked to view the pitchside monitor and he awarded the penalty and Tavernier gave Mitov no chance.

Dessers had a one-on-one with Mitov and rounded the keeper but skipper Liam Gordon shepherded the ball to safety.

The Gers substitute then headed a Tavernier cross against the bar and Lawrence’s shot struck the hand of Luke Robinson and after consulting his pitchside monitor again, referee MacDermid again pointed to the spot and this time Tavernier sent it high into the other corner for his 120th Rangers goal.