The 35-year-old wasn’t a “back up” celebrity waiting in the wings to step in after Jamie Laing was forced to pull out over a foot injury.
“I didn’t anticipate this at all!” he told Radio Times magazine. “I suddenly received a call from my agent offering me the chance to do Strictly and I had to make the decision within an hour or two.
“I was doing a different job towards the end of the year so I had to change my plans, but it was a no-brainer.”
Luckily, Fletcher wasn’t going into the Strictly experience completely blind, having previously been tested for the show before.
“I’d met the Strictly producers previously so they’d already had a taste of me and what I was about," he said. "But I was straight in at the deep end.”
After agreeing to join Strictly, Fletcher found himself partnered with Oti Mabuse – who cried on finding out she would still be taking part despite Laing dropping out.
“I was devastated when Jamie hurt himself and I had a long, tearful conversation with him,” she said. “For a while I thought I had no partner and I was in bed all day thinking ‘I can’t do the show!’ In moments like that you realise how much you love something.
“When they called and told me about Kelvin, I cried. And it turns out he’s incredible!”
Fletcher has lost a few weeks training compared to his Strictly co-stars, but he's confident that it won't affect his performance.
“I certainly don’t feel like I’m at any disadvantage coming in late and I’m used to being the underdog,” he said. “With everything I do, I seem to be the underdog!”
Strictly Come Dancing launches Saturday at 7pm on BBC One. Read the full interview in Radio Times magazine, out now