Tim Ambrose scored a magnificent maiden hundred as two of the county's young guns led a superb Sussex fightback against Yorkshire in the champions' own back yard yesterday.

The 19-year-old, in only his fifth first-class match, played an innings of great maturity to orchestrate their recovery from 40-4, first in partnership with Robin Martin-Jenkins and then with Matt Prior who matched his partner stroke-for-stroke in a thrilling sixth wicket stand of 191 in 43 overs which transformed the first day.

Even Yorkshire supporters stopped grumbling about their own side's shortcomings to acknowledge Ambrose when he hit Craig White to mid-wicket to reach his hundred an hour or so before the close.

He resumes today on 146, having so far batted for a shade over six hours, hitting 19 fours in 273 balls faced. Sussex are 375-6 and in sight of maximum batting points.

You would have got longer odds on Argentina and France being knocked out of the World Cup at the group stage than an Ambrose century when he walked out to bat at Headingley with Sussex 40-3 in the 11th over and the ball jagging about all over the place off the seam.

In three previous innings this season Ambrose has scored 0, 0 and 9, but if he was lacking in confidence he hid it well. It was a struggle for him early on as Yorkshire's seamers beat the bat regularly on a pitch of indifferent bounce.

When Martin-Jenkins was caught off the shoulder of the bat at second slip to give Steve Kirby his second wicket, Ambrose had grafted away for 36 overs for 26 runs. However, he positively blossomed when he was joined by Prior and the pair set about taking the Yorkshire bowlers on.

Any indiscretion in line or length was ruthlessly punished. While Prior drove fluently through the covers to collect the majority of his 12 boundaries, Ambrose despatched anything straying onto his leg stump through square and mid-wicket with increasing confidence.

Prior twice cleared the boundary, first when he despatched a shoulder-high full toss into the new East Stand and then with a top-edged pull off Chris Silverwood which rebounded off the press box window back onto the outfield.

Ambrose batted for a shade under three hours for his 50 but he accelerated until his progress slowed again when three figures were in sight. On 98 a thick inside edge off Kirby flew an inch past his leg stump and perhaps then he knew it was his day. A few moments later he was raising his bat towards the visitors' balcony. It was hard to tell who was more delighted - Ambrose or his equally thrilled team-mates acknowleding an outstanding innings.

The only disappointment was that Prior couldn't reach his maiden hundred as well but on yesterday's evidence it is only a matter of time before he does. Recognition from the England selectors might not be far behind either. Building on the form he has shown in the last couple of weeks, he made 83 off 141 balls with 12 fours and two sixes when White got one to leave him off the pitch.

Their stand broke a 100-year old record for the Sussex sixth wicket against Yorkshire, beating the 179 made by G. Brann and W. Newham at Hove in 1902. It was also the highest sixth wicket partnership at Headingly by any county.

Yorkshire have yet to win a game in defence of their title but they must have thought their luck had changed when stand-in skipper Richard Blakey won a crucial toss and his bowlers reduced Sussex to 70-4 with the new ball. Silverwood uprooted Michael Yardy's off stump and then trapped Murray Goodwin leg before with a shooter after Kirby dubiously had Richard Montgomerie lbw.

Ryan Sidebottom was easily Yorkshire's best bowler and earned an overdue reward when the out-of-form Tony Cottey jabbed a seaming delivery to third slip but that was as good as it got for the Tykes. Gavin Hamilton, an England team-mate of Chris Adams not so long ago, conceded 17 runs in his solitary 12-ball over which contained five wides and a no ball while Katich's two overs of left-arm spin went for 25.

By the close Ambrose was seeing it like a football and Kevin Innes had caught the mood as the pair put together an unbroken seventh wicket stand of 63 in 14 overs.