Another gem of an innings from Michael Lumb could not prevent Yorkshire losing by 166 runs to Derbyshire at Headingley yesterday in their first Championship defeat of the season.

Derbyshire were on top throughout the game and their margin of victory was the highest they have achieved against Yorkshire, beating their 144-run win at Chesterfield in 1990.

If Yorkshire thought they would gain automatic promotion they will have to revise their opinion because they have suddenly gone off the boil, and this reverse came a week after they had crashed at the same venue to their lowest one-day score of 54.

Yorkshire's only grumble yesterday was that the bad weather which had been forecast did not materialise. Play began 45 minuteslate but for most of the day a large circle of blue hung over Headingley.

Chasing an unlikely target of 407, Yorkshire resumed on 12 without loss and never looked like saving the match, despite Lumb's unruffled 86 off 146 balls with ten boundaries.

The left-hander came in at 66 for two and did not depart until the final over, when he was lbw to Mohammad Ali the delivery after a no-ball had spectacularly flattened his middle and off stumps.

It was an astute bowling change by Derbyshire skipper Dominic Cork, who had just re-introduced Ali into the attack and after his first legitimate ball had accounted for Lumb his fourth pinned Steven Kirby lbw to end the match with 21.2 overs remaining.

Until his downfall, Lumb had batted with supreme ease and was unrestrained in his strokeplay. He was deserving of a second Championship century in consecutive matches and in seven innings in all forms of cricket so far this season he has totted up 428 runs at an average of 71.33.

Michael Vaughan also decided to take the attack to Derbyshire when he and Matthew Wood continued their opening stand. As in the first innings England's new one-day captain chanced his luck and on 16 he drove at Kevin Dean and was put down at first slip by Graeme Welch.

Immediately Welch came on to bowl he made amends, his second delivery skidding through and knocking back Vaughan's stumps even though he seemed to have them well covered.

In his next over he cut one in to Anthony McGrath to have him lbw and when Wood's watchful innings was ended by only his second ball from Ali since being flattened by his bouncer at Derby a year ago the game was up.

Although Yorkshire offered no excuses for their defeat, the replacement ball which fired out six of their batsmen in 48 minutes on Sunday was being sent to Lord's by the umpires for examination. The original ball was damaged when hit against railings by Lumb and the replacement swung around remarkably.

A similar thing happened in a recent Lancashire game and it may be that the replacement batch of balls sent out by Lord's has some design fault.

Yorkshire will try to make amends tomorrow when they seek to complete a Championship double over Northamptonshire at Wantage Road. But they will be without Chris Silverwood, who is having an injection on a shoulder injury which has bothered him recently while throwing in from the boundary.

* Ian Bell and Jim Troughton, possible rivals for an England place this summer, both cracked fine centuries to steer Warwickshire to their first Frizzell County Championship win.

Former Durham paceman Melvyn Betts then bagged five wickets to complete a 234-run win against Sussex at Edgbaston.

Bell played faultlessly for his 107 while Troughton, with whom he put on 182, amassed his second ton of the season with 105 in their side's 285 for seven declared.

That left Warwickshire with a lead of 340 but it proved more than adequate as Betts claimed five for 43 as Sussex were shot out for 106, the lowest championship score of the season.