Will Smith recorded his highest first-class score to help Hampshire to a 548 first-innings lead against Lancashire at the Ageas Bowl.
Smith spent nine-and-a-half hours at the crease to score 210 – eclipsing his previous best tally of 201 not out for Durham against Surrey in 2008.
Smith, who is standing in for James Vince as captain in this match, had begun day two on 99, following a day of patient batting on a flat track.
But he turned the dial to three figures with the first ball of the morning – cutting firmly to the boundary for his first ton since September 2014.
The century, from 285 balls was watchful, bordering on sluggish, although an important backbone for his team-mates to play their shots – on a pitch where the only gremlins came when the seam attack bowled a good length.
There appeared no way to see the back of Smith, who had survived a dropped catch on 70, with history showing his two previous centuries for Hampshire both ending unbeaten.
Around him Tom Alsop had departed after facing just five balls of the day as he was leg before to Tom Smith.
Liam Dawson kept the score ticking along with a fleeting 20, before he had his off stump poleaxed by Jordan Clark.
Adam Wheater added some much-needed impetus with a quick 29 from 24 balls – contrasting Smith – but departed driving to Steven Croft.
That brought Ryan McLaren to the crease and started Smith’s second century stand of the innings – after the 191 put on with Jimmy Adams in the first day.
In-form McLaren scored his fourth fifty of the season with a well-paced knock – with 129 put on for the fifth wicket.
Meanwhile, Smith edged towards the second double century of his career and finally reached it with an on-drive.
He soon departed looping Croft up to Simon Kerrigan at wide mid-off for 210.
Lewis McManus and McLaren added extra runs as Hampshire meandered towards a declaration.
The former ticked an edge behind before the latter ended unbeaten on 81, the declaration finally coming after a nicely-controlled hook for six.
Lancashire were given 25 overs to bat in the evening, and lost Smith in the seventh over, nicking Gareth Berg behind.
Berg and McLaren got good bounce and caused problems with the new ball – and the latter should have got on the wicket column when Haseeb Hameed slashed to Mason Crane at point – only for the leg spinner to drop the sharp chance.
Hameed and Luke Procter reached the close 70 for one – still 478 behind, with the follow on set at 399.