Rory McIlroy remained in pole position to be crowned European No 1 for the third time in four years as former supermarket shelf-stacker Andy Sullivan claimed the halfway lead in the DP World Tour Championship.

McIlroy felt he was stuck "somewhere between third and fourth gear" after a second round four-under 68 at Jumeirah Golf Estates in Dubai left him with an eight-under 136, four shots behind Sullivan but crucially ahead of Race to Dubai rivals Justin Rose and Danny Willett by one and two shots respectively.

Englishman Sullivan, a former winner of the Scottish Open Strokeplay Championship during his amateur days, carded a second consecutive 66 to lead by one from Argentina's Emiliano Grillo,

Already the only player to win three times on the European Tour this season, Sullivan could take his official earnings for the year to almost £2million with the first prize of £875,000 and his share of the £4million bonus pool shared between the top 15 players on the Race to Dubai.

Not bad for a man who spent two years stacking shelves in Asda to fund his golf.

"If you ask them they'll probably say I was only there for about six months because I was asleep in the changing room half the time," joked Sullivan, who ignited his round with a “massive” putt for birdie on the 12th before further gains at 14, 15 and 18 hoisted him to the top.

McIlroy has a lead of just 1,613 points over Willett in the Race to Dubai, with Rose more than 600,000 points further back and needing to finish second or better to overtake his Ryder Cup team-mate. Even a victory on Sunday would not be enough for Rose if McIlroy was outright second.

"I'm treating it like a normal event because I'm just here to win and I know if I win, then everything else will take care of itself," McIlroy said. "I'm not quite performing at the highest levels I would like to, though.”

Marc Warren moved up to the fringes of the top-20 with a four-under 68 for a 140. The Glasgow man had four birdies in five holes from the seventh to clamber into a share of 23rd and lead the Scottish challenge.

Richie Ramsay was a stroke back on 141 after a 71 while Stephen Gallacher, a winner in Dubai at the Desert Classic events of 2013 and 2014, had a 72 for his 145 tally.