Fraizer Campbell, newly signed from Sunderland to apply the finishing touches to Cardiff's promotion push, took little more than a minute to celebrate his debut as substitute with the winning goal to restore the Welsh team's 10-point lead at the top of the Championship.

No Cardiff player has scored more than seven in the League, and there was a lingering fear among the Taffia that the lack of a prolific striker could undermine their bid for a place at the top table for the fifth season in succession.

With that in mind, Malky Mackay had his club's Malaysian money men blow the opposition out of the water when others, including promotion rivals Hull City, tried to sign Campbell. Hull matched the £600,000 price on the head of the former Manchester United man, but Cardiff made sure their personal terms were too good to refuse.

The rewards on their latest investment were immediately forthcoming. Introduced from the bench after 61 minutes, the striker England capped only a year ago scored from six yards to make it 11 wins and a draw in the past 14 league games for the Welsh team.

If Campbell was their hero, he was not alone. Leeds would have had a point but for the astonishing reflex save with which David Marshall repelled a point-blank header from Tom Lees late on.

Leeds had the better of a mundane first half in which the first chance was delayed until the 34th minute. Then Ross Barkley, three yards out at the far post, spurned an inviting opportunity by shooting straight at Marshall, who saved with his knees. It was good improvisation by the goalkeeper, but a poor finish by Neil Warnock's temporary recruit from Everton.

For Cardiff, Craig Bellamy prodded the ball past Paddy Kenny just before the interval but had no complaints when the referee's assistant flagged for offside.

Barkley's chance was the sort Steve Morison has been signed to bury but Leeds's new striker from Norwich was unavailable with a thigh strain. Of their other deadline-week signings, Stephen Warnock and Habib Habibou were on the bench, as was Campbell for most of the match because, as Mackay put it: "He hasn't played a lot recently. We knew he had a period of time in him and only that certain period. I put him on because I needed to freshen things up a bit. I'm delighted for him. He is very humble and he has immediately bought into the team ethic. Now we need to get him properly up to speed. At the minute, the mind is willing but the flesh is weak."

Campbell got off the mark by forcing the ball home after Bellamy's initial shot from the 18-yard line had arrowed straight to him. Most goals have defensive errors at their root and this was no exception, young Sam Byram making a hash of a clearance which would have extinguished the attack.

Neil Warnock called it "a schoolboy error, you have to put that in row Z", and insisted Leeds should have had a penalty for a Mark Hudson handball. Dubiously, he said: "Looking at the match, you'd have thought it was us top of the league. I thought the result was very cruel."

Mackay accepted that his team had found it hard going but pointed out that Marshall had been required to make only two saves. He said: "I've never had an easy game at Elland Road, nor against any of Neil Warnock's teams, and with Leeds coming off the back of six home wins we always knew it was going to be tough. But we applied ourselves really well and I'm delighted with another clean sheet. That's five in seven."