The blonde beauty picked up a score of 26 points out of 30 - a pair of nines and an eight - for her and Mark's foxtrot dance, which panellist Bruno Tonioli called ''exquisite''.
He explained: ''You're setting the bar so high that really you have a lot to live up to.''
Len Goodman added: ''It was cracking.''
Katherine wore a yellow sequinned dress for the performance and she was reduced to tears after receiving such praise.
Following her routine, the 30-year-old blonde beauty took to her twitter account to express her joy at the judges' feedback.
She tweeted: ''OMG 2 9's & an 8! Joint top of the leader board! Just called my mum in Wales at 3am to break the news #TellMeImNotDreaming @DancingABC #DWTS (sic)''