The stars, who ended their seven year relationship back in February, were both snapped attending a John Newman performance at The Box nightclub in London's Soho.
According to reports, they spent up to four hours together inside the club, but were pictured leaving separately. Before anyone rushes out and buys a hat, a rep has denied there's any romance between the pair, saying: "It was a coincidence they were both at the same club. Nicole is not back with Lewis."
A source told The Sun: "They arrived separately to watch a John Newman performance and sat at different tables.
"But then they were taken to a private room. John and 5 Seconds Of Summer were in a second one."
The source continued: "The Box's security were not allowed in Nicole and Lewis' room and told to not let anybody else in.
"They stayed well after the club shut. Staff were desperate for them to leave."
Talking about the split earlier this year, Nicole said it was "one of the hardest decisions" she has ever had to make, but her and Lewis "mutually decided" it was best to go their separate ways.
Previous reports have suggested the pair split because Lewis wasn't ready to marry and start a family but Nicole was, although neither have confirmed if this is true or not.
Instead, Nicole has said "everything happens for a reason. I'm a girl of faith and a strong believer, and seven years was a long time" and that she's focusing on a "new chapter in her life". Meanwhile, Lewis publicly told his former flame he would always be "thankful" for the time they had together.
He said: "Through the years we shared a lot, I wouldn't have changed a thing. All the experiences made me the man I'm proud to be right now. The memories together will never be taken away no matter how old we get and I'm thankful for the time we had."
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