LIVINGSTON could not say they had not been warned.

On five different occasions last term, Stevie May rippled their rigging while on loan at Hamilton Academical, so it should have been scant surprise that the St Johnstone striker scored the goal that marked the beginning of the end of their involvement in this season's William Hill Scottish Cup.

This was not the 21-year-old's most impressive performance, but his ability to dictate the direction of a match with one swipe of a boot proved invaluable on an afternoon that was, at times, more uncomfortable for Tommy Wright's side that it ought to have been. The SPFL Premiership side's wayward finishing and Livingston's consequent rise in belief ensured this tie was in doubt until Sanel Jahic's goal gave St Johnstone a cushion and competitive until then end.

John McGlynn spoke of a missed opportunity, but any pretensions the Livingston manager may have harboured about his side earning a place in the next round would have been tempered by their defensive frailties.

The Championship club have conceded at least once in each of their 12 matches since the end of August and had yet to face a forward as accomplished as May, so it was perhaps predictable that he eased St Johnstone's nerves after an even opening quarter.

In keeping with many of his previous 11 goals this term, it was an effort of brutal simplicity. Murray Davidson pushed a ball to him 20 yards from goal and May nudged it to one side before applying a fierce finish that skipped beyond Kevin Walker.

May had already signalled his intentions in the opening moments, skewing over under pressure from the converging Simon Mensing and Jason Talbot.

Nigel Hasselbaink, too, had exercised Walker with an adroit turn and shot after a burst by Davidson, while David Wotherspoon had come close to scoring on three occasions with a header, free kick and angled strike. The goal, then, was the least St Johnstone deserved. While short of their enterprising best, Wright's side controlled the contest, their diamond midfield smothering Livingston's own imaginatively structured quartet and ensuring the play was focused in the visitors' half. That said, McGlynn's side were not without moments of encouragement. Their patient, intelligent passing gave them scope to counter quickly, while they also offered a recurring threat from set-pieces. "At times we were professional, but at other times we were sloppy at both ends," said Wright.

Indeed, the West Lothian side had the ball in the net at one stage only for Marc McNulty to be judged offside, and the striker drew another fine stop just short of the hour then prodded past after a Stefan Scougall run and backheel. Simon Mensing's stoppage-time header kissed the top of the crossbar, but Livingston were unable to break through. "I can't believe we didn't score," said McGlynn. "If we'd got one, I think we might have got another."

Possibly, but St Johnstone underscored their clinical superiority when the chance arose to close out the tie. Davidson beat Walker to a Wotherspoon's near-post delivery and the ball looped into the path of Sanel Jahic to divert over the line. There was still time for May to exhibit his abilities again, cushioning a speared through pass with the outside of his boot and wriggling in front of two defenders before flicking the ball up and nudging a shot goalwards. This time, Walker - helpless in the final moments when Rory Fallon's header scudded the crossbar - was his equal, but by then May had already meted out a familiar punishment to Livingston.