By Rob Barnett at Trent Bridge
Centurion James Hildreth and Nick Compton combined for an authoritative, unbroken partnership of 172 as Nottinghamshire and Somerset moved towards Division One safety.
Hildreth sped to a fluent 102 from 107 balls and Compton was assured in making 62 from as many deliveries after Somerset lost two early wickets.
Their stand took the Trent Bridge visitors to 183 for two in reply to 406 all out on a day shortened to 51.5 overs by bad light and rain.
However, that could matter little after Derbyshire - who need to beat Warwickshire handsomely to stay up at the expense of Notts or Somerset - dropped a bowling point and slipped to 44 for five at stumps. Should Derbyshire fail to reach 200, both Trent Bridge teams will be safe and may well be regardless.
Hildreth and Compton, the latter left out of England's Ashes squad despite touring with them last winter, could ensure the outcome at Derby is irrelevant.
They are on course to share a double-century stand for the second year in this fixture, having added an unbroken 216 in April 2012 when Compton compiled 204 and Hildreth 102.
Their alliance, rescuing Somerset from 11 for two, was similar to the efforts yesterday of centurions Michael Lumb and David Hussey, who put on 214 after Notts were 74 for four.
Lumb and Hussey put the hosts on course for maximum batting points, which the lower order duly secured today.
Following mist and rain that wiped out the morning session, Notts resumed on 378 for seven, aiming to reach 400 inside 14 overs for a fifth batting point to put them half way to safety.
Although Alfonso Thomas trapped Paul Franks in front for 15 with the day's first ball, Brett Hutton and Luke Fletcher eased Notts to their target under floodlights.
Thomas soon wrapped up the innings with two wickets in an over, the first giving Somerset a third bowling point, meaning they needed six more to be safe. Fletcher clipped a catch to Compton on the short leg-side boundary and Harry Gurney was caught behind for nought, leaving championship debutant Hutton unbeaten on 20.
Between innings Derbyshire failed to score a third bowling point at Warwickshire, meaning Notts and Somerset respectively required nine and eight to stay up.
Marcus Trescothick's disappointing season continued as he attempted to drive Gurney but was pinned lbw. Fletcher and Gurney exploited the favourable conditions and the latter saw two appeals rejected before his new-ball partner made the next breakthrough by inducing a thick edge behind from Jones.
In the 14th over Hildreth cover-drove Gurney for the innings' first boundary off the bat as runs began to come more freely.
Hutton's first championship over was a maiden to Compton, who rebuilt alongside Hildreth. The latter clipped Paul Franks to leg for the first of his three fours in the penultimate over before tea. In the next Compton did likewise off Hutton, the first boundary raising a half-century stand.
In brighter conditions after the interval that allowed the lights to be turned off, Hildreth exquisitely cover-drove Gurney to the rope. Compton then edged Fletcher aerially for four in the gap between second slip and gully, moving him to 30 and a trio of Compton fours from Gurney soon ushered Somerset to three figures.
With the lights back on Hildreth deposited Samit Patel's opening delivery, a full-toss, through midwicket to raise his fifty. He then pulled a Fletcher no-ball over the short Fox Road rope and continued to score freely, peppering that same boundary.
Compton hit Patel down the ground for six to reach a half-century after being stuck in the forties. Later in the over Compton cut for four, bringing up a 150-run partnership.
Hildreth clipped Hutton to the midwicket boundary to reach his ton shortly before bad light intervened just after 5pm.