England opener prospects Emilio Gay and Dom Sibley have strengthened their cases to be selected for the Test series against New Zealand with yet more County Championship runs.
Gay made 129 off 189 balls at Lord's - the venue of England's first Test in less than a month - as his Durham side finished the day on 530-8, giving them a 100-run first-innings lead against Middlesex.
The century is Gay's third in four County Championship matches this season, a stunning return that surely cannot be ignored by the selectors in the.
Sibley continued his fine form for Surrey with a huge 187 - taking his average to 62.66 on the year - that boosted his own recall hopes and provided the launchpad for Surrey's huge total of 622 all out, including a debut 120 for 19-year-old Adam Thomas.
Sussex were left 188 in arrears on 76-4 as Surrey go in search of a first win of the season on the final day.
Joe Root - an England batter slightly more sure of his place in the Test lineup - also notched a half-century for Yorkshire as they closed on 365-9 in their second innings to build a lead of 253 against Somerset, setting up a mouth-watering finale in Taunton on Monday.
Elsewhere, Northamptonshire earned their first victory of the season as Ben Sanderson took six wickets from 29 balls in a late surge to help the hosts thrash Worcestershire at Wantage Road.
The Pears were 88-2 in their second innings but slumped to 114 all out to lose by an innings and 177 runs in Division Two, with Sanderson finishing with 7-31. James Sales and Lewis McManus had earlier scored centuries in an impressive partnership of 192 for the seventh wicket as the hosts declared on a massive 597-7.
Kent - led by Chris Benjamin's 123 - seized control against Derbyshire on day three at Canterbury.
Benjamin and Joey Evison helped the hosts to 335 all out in their second innings, making 184 between them for the hosts' seventh wicket.
Derbyshire were 19-1 at stumps, needing 364 to win, after their quick Rory Haydon had taken 5-81 for match figures of 10-163, in just his third Championship match.
Glamorgan's Timm van der Gugten took four wickets as Hampshire were bowled out for 214 at the Rose Bowl. He took two more in their second innings as the hosts slipped to 118-5, needing another 204 to avoid an innings defeat on the final day in Southampton.
