Sam Robson put Middlesex in a commanding position after scoring his third century of the season against LV= County Championship leaders Sussex at Hove.
The 24-year-old Sydney-born opener made 166 as Middlesex ended the second day on 445-5 in response to Sussex's 229, a lead of 216.
Robson has now scored 979 first-class runs and 968 in the Championship and he figured in punishing stands of 120 with Joe Denly and 102 with skipper Neil Dexter to leave Sussex in danger of their first defeat of the season.
Middlesex will also be able to call on Steven Finn when Sussex bat again after he was left out of England's Test team against Australia.
It was a gruelling day for the home attack in stifling heat, although Australian Steve Magoffin took two more wickets and now only needs three to become the first bowler to reach 50 for the season.
Middlesex built a solid platform by scoring 120 runs in the morning session for the loss of just one wicket when Dawid Malan edged a lifting delivery from Jimmy Anyon behind for 30.
In contrast to Robson, Denly has been in poor form and he made the most of a let-off on 31 when he was put down by Chris Nash at short leg off Magoffin.
Denly made the most of his reprieve to score 87 with 12 fours and a top-edged six off Chris Jordan, his highest score of the season, before he was caught at short midwicket off the third ball after lunch to reward the persevering Magoffin.
Anyon returned to the attack to have Adam Voges caught at short cover off a top-edged pull but Middlesex regained the initiative in a stand of 102 for the fourth wicket between Robson and Dexter for the fourth wicket.
Dexter had moved to 48 when Magoffin took the new ball and knocked back his off stump but Robson looked in supreme form, both against the seamers and Monty Panesar.
The left-arm spinner was economical but struggled to make any inroads before Robson, having just lofted him over the long on boundary for six, came down the pitch looking to repeat the shot and was bowled by a delivery which kept very low. His 166 contained 22 boundaries and came off 261 balls. He batted for more than six hours.
Gareth Berg was dropped on nine when Nash appeared to lose sight of the ball in the sun as he ran in from the square leg boundary and by stumps he and John Simpson had put on 51 for the seventh wicket.