IF Graham Thorpe's retirement has left the door to the Ashes series ajar then Paul Collingwood is doing everything in his burgeoning powers to make sure he is in prime position to step through it.

Kent might think they hold the Key to the door, but the burly shape of Robert Key does not offer the all-round qualities of Durham's latest record-breaker.

Watched by chairman of selectors David Graveney, Collingwood yesterday became the first batsman to score four championship hundreds in a season for Durham when he followed his 190 at Derby last week with 181 not out against Somerset at Taunton.

He also scored centuries home and away against Worcestershire, and as the latter came in his last game before the one-day international series he has now made hundreds in the three successive championship appearances.

With Mike Hussey making 63 and Gordon Muchall 57, Durham took another big stride towards promotion by amassing 345 for three before bad light ended play 25 minutes early.

Such a total didn't look likely in the first half hour, when Andrew Caddick and South African Charl Langeveldt found disconcerting bounce and movement and must have fancied three or four early wickets.

But perhaps they got a little excited as after six overs they stopped putting the ball in the right place and after being beaten by the first ball he faced Collingwood quickly assumed supreme control.

His only hiccups came on 21, when he offered a sharp low chance to gully off Caddick, and on 148, when Richard Johnson had to turn and run 15 yards from mid-off to get under a miscued straight drive but couldn't hang on.

Otherwise Collingwood gave the perfect demonstration of how to catch a selector's eye, not least in his refusal to be drawn into anything rash by 22 overs of largely negative left-arm spin from Ian Blackwell.

Although Graeme Smith is playing in his last match before returning to South Africa, Somerset have appointed Blackwell captain for the rest of the season with immediate effect.

He had himself on as early as the 19th over, which was tantamount to admitting that the seamers had missed the boat with the new ball.

Bowling over the wicket, there were at least three balls an over which Collingwood could kick away outside leg stump. But he never missed an opportunity to strike, driving Blackwell for his only six to move to 95.

The 90s hold no fears for him now and after taking a single he reached his 158-ball century by on-driving Johnson for his 12th four.

Shortly afterwards he took three fours in an over off Johnson with a back-foot punch through the covers, a leg glance and a straight drive. But there was never any hint of getting carried away as he continued to play with a measured calm.

After Hussey won the toss Collingwood went to the crease in the third over, when the early threat saw Caddick have Gary Scott caught by the third of five slips.

Hussey looked fortunate to survive an lbw appeal by Langeveldt when he was on one, but the bowlers' over-eagerness to capture a key wicket saw the runs suddenly start to flow.

It was 74 for one when Blackwell came on, but the closest he came to success in a 22-over spell broken only by lunch was when he turned one between Hussey's bat and pad and just missed off stump with the captain on 35.

Hussey made one of his three triple centuries for Northants at Taunton and it was a surprise when he shouldered arms to Caddick and was lbw shortly after lunch.

The second wicket stand was worth 142, then Muchall played a nicely-tuned second fiddle in a partnership of 152. It was also a surprise when he fell, pulling the innocuous medium pace of Keith Parsons to long leg.

If it was a sign of desperation that Parsons was bowling, it was even more so when the left-arm spin of Arul Suppiah then Smith's off-spin were tried.

It was off Suppiah that Collingwood was missed on 148, Johnson tipping the ball for two runs, and there had been nine fours in the batsman's third 50, which came off only 48 balls.

He then throttled back, clearly determined to go at least one better than at Derby, where he equalled his career-best.

He also had to survive a good new-ball spell by Langeveldt, who nipped one back sharply, narrowly missing off stump.

Unfortunately, if the weather forecast is accurate, Collingwood will have to wait for the chance to complete his double century and Durham might have to settle for another draw as they cannot afford much lost time on the traditionally good Taunton pitch.

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