Middlesex 445 for 5 (Robson 166, Denly 77) lead Sussex 229 by 216 runs

Middlesex's day began well with the news that a tall, understandably upset fast bowler was on his way to pep up their attack - and then it just got better and better, thanks to another rock-solid innings from the hugely impressive Sam Robson.

Steve Finn's omission from the second Ashes Test could yet prove to be decisive so far as this contest is concerned. "Gutted not to be playing," Finn tweeted before leaving Lord's to drive to the south coast, where he replaced Gurjit Sandhu in the visitors' line-up.

Middlesex will hope that any lingering annoyance or frustration felt by Finn will be taken out on Sussex during the remainder of this match. And despite Robson's best efforts to suggest that this pitch is a featherbed, a surface still producing steep bounce should be right up the England 12thman's street.

"All the guys were pretty gutted for Steve Finn when he was left out by England this morning," Robson said. "But I think he'll be a handful for Sussex here. The pitch does have some pace and bounce and at times it was pretty hard work batting today. Given the context of the game and the fact we really wanted a good lead, I think this was probably my best hundred of the season."

Whatever the outcome, and regardless of how Finn bowls, it will take something spectacularly special to dislodge Robson from the role of star man in a game that could see Championship leaders Sussex suffer their first defeat of the campaign while putting Middlesex right back among the title favourites.

True, Ed Joyce batted beautifully on Wednesday in making an elegant hundred for Sussex. Even that innings was put in the shade, though, as Robson blunted the dangerous home attack for hour after hour while scoring his third century of a wonderfully profitable season.

A good number of deliveries, rearing past the outside edge, were simply unplayable. But Robson chased nothing, shrugged off those balls that beat him and, with his splendidly tight technique evident throughout, accumulated runs so assuredly that Sussex were left close to despair well before the close.

The 24-year-old opener - born in Sydney but only 12 months away from qualifying for England on residency grounds - came into this contest with 802 Championship runs to his name. By the time he trudged away in the evening, finally dismissed for 166 after six-and-half hours at the crease, that total had soared to within touching distance of four figures, leaving him alone at the head of the run-scoring charts.

With Chris Rogers now playing for Australia, the responsibility on Robson to hold the Middlesex innings together has increased a notch or two. But on the evidence of this performance, the more pressure they put on him the better. As an example of how to open and anchor an innings while scoring at a perfectly decent clip, it could hardly have been bettered.

Sussex perhaps missed a trick on the first evening when they bowled too short, too often during a 13-over session that saw the visitors reach 44 without loss. In any event, their three-pronged pace attack of Steve Magoffin, Jimmy Anyon and Chris Jordan was made to sweat buckets under a burning sun today in order to add only modestly to their pre-match aggregate of 120 Championship wickets.

Dawid Malan, who has struggled in four-day cricket this season, did fall early to one from Anyon that lifted and left him. But that merely allowed Joe Denly to complement Robson perfectly during a rollicking stand of 120, in 27 overs, for the second wicket.

Denly did most of the scoring - a Championship best of the season 77 - throughout a passage of play where almost every delivery seemed to either beat the bat or race across a brown outfield for four. The No. 3 led a charmed life at times (he was dropped at short leg on 31) but his attitude of making hay before something came along with his name on it paid valuable dividends.

Even at 180 for 2, Middlesex did not appear guaranteed a lead but Robson's stands of 50 with Adam Voges, 102 alongside Neil Dexter and 62 with John Simpson enabled the advantage to grow into match-winning proportions.

Driving fluently whenever the opportunity arose, Robson reached 100 from 183 balls, 150 from 245 and was finally out - bowled while advancing on Monty Panesar - by the 261st delivery he faced, having just hoisted the spinner for a six to add to 22 fours. It had been an innings to cherish.

As for Sussex, they have been in tighter spots this season - most obviously against Middlesex at Lord's in early June when they were made to follow on. But this pitch, and these hungry opponents, will take some subduing.