Buoyed by Ian Harvey and Tim Bresnan's record-breaking eighth wicket partnership, Yorkshire took an even firmer grip on Somerset by making the visitors follow on, 319 runs in arrears at Headingley yesterday.
By the close they had reached 109 for four - still 210 behind - which left Yorkshire on the brink of an overwhelming win in their first home Championship match of the season, despite the first day of the game being wiped out by the weather.
Harvey and Bresnan's stand was already worth 174 when Yorkshire resumed in the morning on 401 for seven and 100 runs were added in 75 minutes before the declaration came at 501 for nine.
Bresnan was first out, bowled by Aaron Laraman for a career-best 74 off 149 balls with six fours and two sixes, his alliance with Harvey worth 238 in 52 overs.
It was Yorkshire's best in a home match for the eighth wicket and surpassed only by the 292 between Bobby Peel and Lord Hawke against Warwickshire at Edbaston in 1896.
Matthew Hoggard's straight drive into the hands of Nixon McLean left Harvey unbeaten on a sparkling 209 after five hours of glorious batting in which he struck 30 boundaries off 234 balls.
Harvey's effort left him just four runs short of equalling Herbert Sutcliffe's 213 at Dewsbury in 1924, which is the highest score by a Yorkshire batsman against Somerset.
The day started badly for Somerset who found themselves without captain Marcus Trescothick, who had returned home to Taunton because his wife was ready to deliver a baby sooner than expected.
John Francis opened the Somerset innings in Trescothick's absence with debutant Sanath Jayasuriya, but the Sri Lanka Test batsman whipped his third delivery from Matthew Hoggard to mid-on where Craig White dived to his right to pull off a breathtaking catch.
From then on it was South African Deon Kruis and Bresnan who combined to knock the stuffing out of Somerset with three wickets apiece.
Kruis picked up his first scalp for Yorkshire when Matthew Wood held on to a fast catch from Francis at second slip.
Harvey, suitably rested, came on at 149 for seven and picked up the last two wickets as Somerset slumped to 182 all out.
Their second innings began even more woefully with Kruis wreaking havoc by grabbing three wickets in nine deliveries without conceding a run.
Jayasuriya completed a nightmare debut by slashing his 11th ball straight to Richard Dawson at backward point and in his next two overs Kruis had Michael Burns caught behind off one which lifted and pinned James Hildreth lbw.
White had his first bowl of the match at 36 for three and it was a shrewd move by the captain because his third ball was edged by Ian Blackwell to Ismail Dawood who held on to his fifth catch of the day.
Somerset were 37 for four and Yorkshire were sniffing a two-day win, but Francis and Laraman offered resistance and were still together at the close.
Commenting on his wickets, Kruis said: "It was brilliant to get my first victims for Yorkshire and this has taken some of the pressure off me.
"I thought I bowled well at Chelmsford last week without any luck but luck has been with me in this game and all I want now is for us to go on and win the match."
* There was drama of a different kind during the morning when a man walked on to the pitch and refused to leave. He was escorted off by stewards and arrested for trespass but had still not been charged last night
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