Kiran Carlson (170*) and Chris Cooke (133*) entered the Glamorgan records books with an unbroken partnership of 307 as the Welsh county dominated three of their LV= Insurance County Championship match against Northamptonshire.
The pair broke the previous club record county fifth-wicket stand of 264 set in 1949 as Glamorgan reached 462/4 at the close, 247 runs ahead of the visitors.
"Chris and me put on a great partnership there, it was nice to bat with him and always nice to score runs, great to do it with the skipper and to put the team in a good position," said Carlson.
"Marnus and Billy both batted brilliantly for their partnership earlier, and set the platform for us. Chris and me set our stall out to bat for a long time, we knew there were runs to be had.
"It's great to be in the record books though you don't think about it while you're batting, lovely for Chris and me to share that record.
"We'll have to see in the morning the best route to take nine wickets to try to win the game- I'd prefer to do that than get a new career-best (currently 192)."