Alviro Petersen and Ashwell Prince shared an unbeaten partnership of 321 as Lancashire took firm control on day one of their LV= County Championship Division Two clash with Glamorgan
Petersen, a former Glamorgan captain, scored 205 and is just five runs short of his career best score in the Championship which was 210 for Glamorgan against Surrey four years ago.
Prince, meanwhile, played a majestic innings, reaching his fifth century of the season and at the close he was undefeated on 154.
Their efforts took Lancashire, who won the toss and chose to bat first, to 425 for two at stumps as they made the most of the conditions at the picturesque Penrhyn Avenue.
Glamorgan actually got off to a decent start, with Michael Hogan trapping Paul Horton lbw for one in the seventh over before David Lloyd bowled Karl Brown for 54 shortly after lunch to put Lancs on 104 for two.
But that was as good as it got for the home county as the third-wicket pair went on the rampage.
When they added 246 they broke the previous record for the third wicket against Glamorgan set by Graeme Fowler and David Hughes at Old Trafford in 1983.
Petersen and Prince soon passed 50, with Prince notching his ninth half century this season, and the former soon reached another milestone as he clocked his third century of the campaign.
Prince, who is having his best season for Lancashire, has now scored 1,108 first-class runs for the Red Rose county and if he does not return next season it will be a huge loss for Lancashire who are almost certain to return to Division One.
There was nothing in the pitch for the Glamorgan attack and the omens were not good when wicketkeeper Mark Wallace stood up early in the innings to opening bowler Graham Wagg.
Petersen again showed his liking for the ground and during his short career with Glamorgan he made 144 against Lancashire in a 40-over game.
The new ball came and went with Prince majestically driving Michael Hogan for three fours in succession in an arc between mid-off and cover point.
After passing 150 the next target for Petersen was his double century and he achieved this by glancing Dean Cosker down to the fine leg boundary.
Petersen was delighted with his display but refused to get carried away, saying: “Days like this in cricket don’t come often, when you are in you try and kick on to make it count.
“It was an important day for the boys but tomorrow is a new day and it brings new challenges.”