Comedian Robert Webb and his dance partner, Dianne Buswell, are withdrawing from Strictly Come Dancing.
Peep Show star Webb, who had open heart surgery two years ago, made the decision due to ill health.
He said he had an urgent consultation with his heart specialist after experiencing symptoms and she recommended he pull out of the series.
A Strictly spokeswoman said the BBC One show would continue as normal this weekend, despite Webb's departure.
Webb, 49, said he was "extremely sorry" to have to leave the competition, adding: "It became clear that I had bitten off way more than I could chew for this stage in my recovery."
"I'm proud of the three dances that Dianne Buswell and I managed to perform and deeply regret having to let her down like this," he said.
"I couldn't have wished for a more talented partner or more patient teacher, and it's a measure of Dianne's professionalism and kindness that I was able to get as far as I did."
He thanked everyone who had voted for him and his dance partner, saying he was "especially touched" by the support from fellow heart patients - and that he had perhaps been "too eager to impress them".
He said they would know "that recovery doesn't always go in a straight line", adding that "it was always going to be a difficult mountain to climb".
"I leave knowing that Strictly viewers are in very safe hands and I'll be cheering for my brother and sister contestants all the way to Christmas," he said. "Despite this sad ending, it has been a genuine honour to be part of this huge, joyful and barking mad TV show."
In a video played on BBC Two's It Takes Two, which announced the news, he said he would "miss learning new dances and being able to do new dances... it's been a ride".
Buswell said she was a "massive fan" of Webb's, had been delighted to learn he was joining the show and being partnered with him was the "icing on the cake". She said they had worked hard "and had a good laugh along the way".
She added: "I know Robert had a lot more to give to the competition but his health of course comes first and I wish him a speedy recovery. I feel lucky to have danced with him and to call him a friend."
Fellow contestants also sent their best wishes, with BBC Breakfast's Dan Walker saying it had "been wonderful to watch them enjoying every dance each week".
Strictly's executive producer Sarah James thanked the pair for the "commitment, creativity and joy they brought to the show".
She said they were "so sad" but completely understood and supported his decision, adding that everyone on Strictly sent "love and best wishes for his continued recovery".
Webb and Buswell had performed three dances together, most recently as Kermit and Miss Piggy in last weekend's Movie Week show.
They danced a quickstep to The Muppet Show theme, from The Muppets Movie, on Saturday night and scored 25 points from the judges. Viewers gave them enough votes to avoid the dance off, broadcast on Sunday.
Webb, who previously became a fan favourite with a Flashdance routine on Let's Dance for Comic Relief, had said it was his health condition that made him want to sign up for Strictly.
"It's partly my age, and it's partly that nearly two years ago I had quite a big-deal health thing," he told the BBC before the live shows began. "I had to have open heart surgery, so since then I think my attitude is basically, this is no time to be cool, sitting at the edges watching the other people do the dancing."