Dumfries & County’s Marchbank, last week’s winner of the Stephen Gallacher Foundation Scottish Boys Stroke Play Championship, continued his form to oust McDonald around 8pm tonight on the final green. After an engrossing battle, it was the tie of the week so far.

McDonald, who reached the semi-finals of The Amateur Championship and played all four rounds of the Aberdeen Asset Management Scottish Open on The European Tour, birdied the 12th to go one up before SGU National Boys’ Squad player Marchbank responded in style.

The 18-year-old, winner of the Boys’ Order of Merit last year, fired his six-iron into the cup on the 180-yard 13th for the second hole-in-one of his playing days.

“It was very handy to do it and square the match,” said Greig, who meets Christopher Young of Cardross in the last-32 tomorrow. “I played pretty solidly and kept my form going.

"Jack won the 14th but I took the 16th and 17th before we halved the last. It’s a good win but I’m taking it one round at a time."

With No. 3 seed McDonald knocked out, only two of the eight seeds remain – Graeme Robertson and Matthew Clark.

The top seed, Glenbervie’s Robertson, was the first man to book his place in the last-32 after a 3&2 success over Alasdair MacLennan (Kings Acre).

The University of Stirling student, 24, was down early on before quickly fighting back to set up a last-32 clash with Troon Welbeck’s Charlie MacNeal, victorious over Chris Robb (Meldrum House) by 2&1.

“I’m not really feeling any extra pressure as the top seed,” admitted Robertson, who showed his match play credentials with an impressive singles success in Europe’s Palmer Cup win.

“I’m playing well and the course suits my eye. I’m comfortable shaping the ball both ways which you need to do around here.”

Clark of Kilmacolm, the recent winner of the Newlands Trophy, continued his bid for glory by seeing off Grant Minnes (Kirkintilloch) by 4&2.

Elsewhere, Craig Ross of Kirkhill claimed a notable win, edging out the No. 4 seed Paul Ferrier of Baberton despite almost throwing success away.

Ferrier was in superb knockout form to reach the semi-finals of The Amateur Championship at Royal Troon, but was immediately in trouble against Ross, who was a commanding five up at the turn.

Ross, fifth in the Golf Data Lab Scottish Youths and a member of the Scottish Golf Academy, said: “I nearly let it go. It was back to one up for me on the 17th and it was a wee bit nervy. But I got through 2&1 in the end.”

Callum Trahan (Meldrum House) is Ross’ fourth-round opponent, after he impressively eased past Jamie Binning of Ranfurly Castle 5&4.

James White, like Robertson a SGU National Men’s Squad player, didn’t feel he was at his best as the Lundin man edged out Meldrum House’s Nick Robson.

White, beaten in an epic quarter-final tie by James Byrne at Western Gailes 12 months ago, said: “I managed to survive. The conditions were tough and the wind never seemed to be helping.”

White now meets Gordon Stevenson (Whitecraigs), while other last-32 ties feature James Ross of Royal Burgess – a 4&3 winner on three occasions – against former Lothians champion Alexander Culverwell (Dunbar). Play in the fourth round begins tomorrow at 8am.