Lyth, Yardy and Mitchell hit tons
Adam Lyth's 104 put Yorkshire in charge of their clash with County Championship champions Durham, while Michael Yardy also scored a ton.
The White Rose prospered having elected to bat in a tussle between last year's top two, which had on display nine players with a combined 299 Test match appearances between them.
But it was a 26-year-old with no international experience who stole the show, scoring the first century by a visiting player in the opening innings at Chester-le-Street in a championship game since 2011, when Vikram Solanki hit 124 for Worcestershire, as Yorkshire posted 299 for three.
An unbeaten century from Michael Yardy just about gave Division One leaders Sussex the upper hand against Lancashire on the first day at Old Trafford.
The England batsman's 132 not out provided the mainstay of the visitors' 276 for eight, being the primary factor in them recovering from 176 for seven.
He was involved in the only two significant partnerships of the day, putting on 80 for the second wicket with Chris Nash - now recovered from a ruptured appendix suffered in pre-season and captaining the side in the absence of Ed Joyce away on international duty with Ireland - and 74 with Jimmy Anyon for the eighth wicket.
Middlesex lurched from the high of a record run-chase last week to being humbled in a devastating morning session from hosts Warwickshire.
Having beaten Yorkshire at Lord's last Wednesday, knocking off a target of 472, they slid to the opposite end of the scale at Edgbaston.
Electing to field after winning the toss, they were reduced to 66 for eight before lunch, so the fact they recovered to post 167 in the afternoon could be considered something of a success.
Samit Patel again showed his liking for batting at Taunton as his unbeaten century helped Nottinghamshire take full advantage of being sent in by Somerset as they closed day one on 382 for five.
Only 10 championship hundreds had ever been scored by Nottinghamshire players at Taunton coming into the match, with two of those being recorded by Patel, who made 104 in 2009 and 128 two years later.
And the 29-year-old all-rounder was at it again on Sunday with 116 off 149 balls, including 20 fours, to leave the visitors in a strong position after the opening day as they chase a first championship win at this ground since 1985.
A fifth-wicket stand of 154 stand between James Foster and Mark Pettini put Essex in a strong position only for Nathan Buck to fire Leicestershire back into contention with two late wickets on day one of their Division Two match at Chelmsford.
The Essex pair came together with the score at an uncertain 75 for four and proceeded to dominate the visiting attack before Pettini finally fell for 71.
Captain Foster was out from the final ball of the day for 82 as the two dismissals, both from Buck, pegged the home side back to 254 for six at stumps.
A defiant unbeaten century from captain Daryl Mitchell gave Worcestershire hope on the opening day of the clash with Glamorgan as they closed on 232 for nine.
Mitchell reached 101 not out off 294 balls, notching 11 fours along the way, but he received little support from his team-mates as Glamorgan's Graham Wagg and Dean Cosker finished with four wickets apiece.
Adam Riley took four wickets as Kent reduced Surrey to 276 for eight on day one of their clash with Surrey at Canterbury.
The 22-year-old mixed up pace and flight to good effect as his spin claimed the wickets of the three highest scorers of the day, catching out Jason Roy, who top-scored with 60, Zafar Ansari (48) and Aneesh Kapil (38). The trio had helped their side recover from a slow start.
Riley finished the day with four for 77.