If Sussex come up short in their bid for the Championship they may well look back on yesterday as the day their challenge started to unravel.

While Lancashire were inching towards a superb come-from-behind victory over Nottinghamshire and Hampshire were hammering Yorkshire with a day to spare, the leaders lost all ten first wickets in an astonshing afternoon session at Edgbaston.

Sussex must have fancied their chances of at least getting close to Warwickshire's 375 when Richard Montgomerie and Carl Hopkinson launched the reply with a confident opening stand of 87 in 20 overs.

But in the space of 18 balls immediately after lunch five wickets fell for six runs and, although Chris Adams and Matt Prior staged a recovery of sorts to avert the follow-on, Sussex lost their last three for two runs to concede a deficit of 129.

Sussex bowled well after tea. James Kirtley and Yasir Arafat struck with the new ball and Robin Martin-Jenkins made a big breakthrough just before the close when he extracted some bounce to defeat Nick Knight.

But opener Ian Westwood was badly missed at slip by Mike Yardy off Mushtaq Ahmed and Warwickshire will resume today on 88-3, a lead of 217.

Sussex will be entitled to call themselves champions-elect if they can extricate themselves from this mess and end their 23-year wait for a victory at Edgbaston.

The more likely scenario, on a pitch which is not going to get any easier from here on in, is only a second Championship defeat of the season.

That would not be a terminal blow to their hopes but it would make next week's top-two showdown against Lancashire at Hove even more important.

Left-armer Neil Carter was the chief beneficiary of the collapse. He took three of the first five wickets and then mopped up the tail to lodge his best Warwickshire figures and his first five-wicket haul for three years.

Although the odd ball lifted disconcertingly off a length, conditions were fairly benign which made Sussex's performance even more surprising.

Heath Streak and Carter made little impact with the new ball but when Carter returned after lunch the complexion of the contest, and perhaps Sussex's season, suddenly changed.

Hopkinson was his first victim, beaten by a beauty which pitched and straightened.

Carter then struck with successive balls as Murray Goodwin got the feintest of edges when Carter went around the wicket and Martin-Jenkins was bowled off his pads by a full-length delivery ideal as a first nut for a tall batsman.

It was high-quality seam bowling but Montgomerie and Yardy were guilty of poor shot selection at the other end.

Montgomerie upper-cut to third man when well set and Yardy chased a ball outside his off stump to give James Anyon his second wicket in successive overs.

At that stage the follow-on target of 226 looked a long way off but Prior launched a typically robust counter-attack which brought him a half-century off just 44 balls including 11 boundaries.

He showed few ill effects of the hamstring strain which forced Sussex to call-up reserve wicketkeeper Andrew Hodd for the rest of the match.

But it was never going to last. After helping his captain add 86 in 11 overs Prior got a leading edge to cover trying to pull slow left-armer Paul Harris through the leg side.

Arafat is another player who loves to attack but he played with commendable restraint to make sure Sussex avoided the follow-on, lofting Alex Loudon onto the top tier of the pavilion before flat-batting a drive to cover.

Adams passed 50 for the sixth time this season before his only false shot cost him his wicket when he swatted a long hop straight to cover to give Carter his five-for.

Jason Lewry lost his middle stump to the next ball as he backed away, an odd shot to play when another precious bonus point was just four runs away.

Warwickshire had lost their last three first innings wickets adding 46 in the first hour. Kirtley finished with 3-78, his best Championship return of the season, while Arafat claimed two more victims to make it 21 in four games.