With good weather gracing the opening three days of the English summer at Lord's, Middlesex and Nottinghamshire head into a fourth with promises of a tantalising day's play. Much of that is down to a smart finish to the Middlesex first innings thanks to a fine hundred from John Simpson, a good spell from Steven Finn and a fine counter-attack from Notts' own Chris Read.

It was Simpson's first century since April 2011; then, he was part of a side that would romp to promotion - one of a number of batsmen in a rich vein of form. That first season up in Division 1 saw him struggle badly, his summer average plummeting from 42.66 to 15.50, while others saw little difference in theirs. He did not even pass fifty, and, going into 2013, the chat among Middlesex fans was of slowly working the talented yet raw Adam Rossington into the XI, eventually, at Simpson's expense.

He responded with a fighting 97 in the opening game of last season - at Trent Bridge against Nottinghamshire, no less - which remained his highest score of the campaign, as Rossington cut his teeth in limited overs cricket. It was one of five half centuries for Simpson, as the 2012 average was almost doubled and some respite was earned. Still, three figures remained elusive. It makes the manner of his celebration of this century, brought up with a fine cut behind point, poignant.

As the ball rattled into the Grand Stand railings, his arms sunk by his side, before reanimating to remove his helmet and raise his bat to acknowledge the acclaim from the fans and his own dressing room. There was no punch of the air or audible yelp to signify the release of pressure built up over three years. Not even the satisfaction of knowing a winter of working on a clear game plan, along with the technicalities of a preliminary movement and lighter feet, with batting coach Mark Ramprakash, had paid off. This was pure relief.

"It's really nice to contribute," he said, high in spirits but exhausted after spending all 93.5 overs of the day on the field. An affable and humble guy, he revealed that his first port of call this morning was to see Robson past the 150 mark. Then it was time to focus on his own game - something he's been doing for a while now.

"Going through that little period in 2012 when we did get promoted was tough. Last year was mixed emotions really - getting quite a lot of fifties and not really going on. I've worked hard during the winter with Mark Ramprakash and really tried to move my game to the next level. Just trying to have a real focus and real clarity with every ball."

Apart from his own accomplishment, Simpson's 242-ball stay at the crease allowed Middlesex to reach 439. He began day three scratchily, scoring the 18 runs he needed for fifty with thick edges and good fortune.

At the other end, Sam Robson began with the ease and comfort of someone seeing out a duvet-day on their couch. Another milestone with little fuss, before Simpson pushed the home side into a first innings lead. Two overs later, Andy Carter got one to leave Robson at the last moment and take his edge through to Rikki Wessels at first slip to end the England hopeful's effort on 163.

A brace of wickets either side of lunch - Steven Mullaney toppling Ollie Rayner's middle stump and Samit Patel yorking James Harris - sparked a brief fight back. But with the help of some agriculture from Tim Murtagh, some power from Finn and a free license for Simpson, a useful lead was established.

Gareth Berg, originally due in at seven, was unable to bat after spending the day in hospital, having woken up to discomfort in his right arm. It is also worth noting that Peter Siddle's first innings of Championship cricket saw him go 25 overs without a scalp to his name. He will no doubt be eyeing some of great worth tomorrow.

Notts' deployed the heavy roller before their second innings but neither the sting of Middlesex's 113-run lead, nor the variable bounce were squeezed out of the surface. Still, only Phil Jacques can say with great certainty that he fell victim to the latter - hanging back to a good length ball from Steven Finn, which ducked just under his bat to hit him flush on the pads.

But the indecision was there, as later both James Taylor and Samit Patel fell in similar fashion, to the same bowler. However, unlike Jacques, they could probably pocket more of the blame for their dismissals.

Murtagh had two lbws of his own to see off Mullaney and then Michael Lumb, who was lucky to have still been there. Earlier, he misjudged a hook against Finn, for the second time in the match. Eoin Morgan at point left it for Finn, whose body language suggested he had already left it for Morgan. Meanwhile, Lumb had begun a sombre walk off, before reluctantly deciding to wait around for what should have been his end. Morgan's belated attempt to catch the ball required a dive and, alas, a chance was spurned.

It cost them 20 runs but perhaps a more expensive missed opportunity came in the penultimate over of the day, when Notts skipper Chris Read crunched Finn at bat-pad, who could not take it. Catches in that position rarely come more difficult, but it would have been a valuable snare. Read had entered at 120-4, with the lead at just seven, and took the game to the bowlers as he so often does.